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  • Life and Medical Sciences  (172)
  • Earth model, also for more shallow analyses !  (22)
  • AERODYNAMICS
  • Animals
  • 1925-1929  (195)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 42 (1926), S. 523-560 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The different kinds of scales characteristic of the adult sturgeon are described and the facts of ontogenesis which throw light on the history of these structures are presented.The scales of Acipenser are exclusively mesenchymatous and therefore are not morphologically comparable with the placoid scales of elasmobranchs. Salensky ('80) drew erroneous conclusions as a result of failure to study the earlier stages of ontogenesis. Goodrich ('03) has correctly described the ontogenesis of the lepidotrichia.The original form of ganoid scale was that of an elongated rhomb with a longitudinal crest on its external surface. The various forms of scales of the adult sturgeon have been produced by the differentiation of such a scale by change in size, shape, and the fusion of the different elements.The conclusions are extended to the entire family of Acipenseridae.
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  • 2
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The study is divided into three parts. Part I deals with the chromosome number and morphology in the amniotic cells of rabbit embryos. The number of chromosomes has been found essentially constant in amniotic cells of young, but more variable in older embryos. The somatic number is 44. Part II deals with the chromosomes of race crosses (Flemmish Giant X Polish) in which the homologous chromosomes were found to be alike. Part III deals with spermatogenesis. There are forty-four chromosomes in spermatogonia, and twenty-two in primary spermatocytes. The sex chromosomes are of the usual X-Y type.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 43 (1926), S. 45-54 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The spermatogenesis of the domestic mouse has been studied. There are forty chromosomes in spermatogonia and twenty in primary spermatocytes. The sex chromosomes are of the usual X-Y type. Especial attention has been devoted to the study of chromosome morphology, both in spermatogonia and in primary spermatocytes.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 43 (1926), S. 81-103 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Paramecium trichium varies from 50 μ to 105 μ long with most individuals between 80 μ and 90 μ. The width varies from one-third to one-half the length. It is somewhat depressed dorsoventrally. The broad buccal groove extends from the anterior left border diagonally across the ventral surface to the mouth, which is usually slightly anterior to the middle and to the right side of the median line. The mouth leads into a relatively long cytopharynx containing an undulating membrane. The cytopyge is subterminal and the small caudal tuft of longer cilia is subapical. The plastic ectosarc contains numerous trichocysts. A contractile vacuole apparatus occurs near either end. Each is deeply located and stains more intensely than surrounding protoplasm. In life there appear to be two alternately contracting vacuoles with smaller ones adjacent. Contractions are from fifteen to twenty-five per minute. The macronucleus is medium in size and the single micronucleus is of the ‘caudatum’ type.Binary fission appears to be initiated by a metaphase-like condition of the micronucleus. This is followed by great enlargement and the eventual separation of the chromatin threads into two anaphase groups. The metaphase thus appears to precede the changes which correspond to a prophase in other cases. During division of the body, the two old contractile vacuoles persist as the posterior ones for the daughters, new anterior ones being developed.
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  • 5
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the epidermal cells of green-frog tadpoles (Rana clamitans) there are present coarse, conspicuous mitochondrial threads. In the dorsal body regions, epidermal cells of the middle layers also contain pigment granules, grouped in crescentic masses in the distal portions of the cells.Administration of thyroid extract results in permanent disappearance of the mitochondrial threads and disappearance to a large extent of the epidermal pigment granules. Processes of cellular dedifferentiation and proliferation occur rapidly over widespread areas, the mitochondria undergoing intracellular resorption. A new type of epidermis is developed containing many cutaneous glands, adapted for the approaching terrestrial life.Wound infliction induces similar processes of cellular dedifferentiation and proliferation in the epidermis in the immediate vicinity of the wound. Cells in this region lose their mitochondrial threads by intracellular resorption, and there is also some disappearance of pigment granules. The new epidermal cells in the early stages of regeneration produce neither mitochondrial threads nor pigment. This condition is not permanent, however, and in the later stages the larval characteristics appear again, both mitochondrial threads and pigment being redifferentiated.In the hyperthyroid animals there is also a significant mobilization of mesenchymal chromatophores, correlated to some extent with the loss of epidermal pigment.The significance of epidermal changes is discussed with reference to cutaneous abnormalities associated with hyperthyroid and hypothyroid conditions.
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  • 6
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: 1Monovalent cation salts induce reversal in the direction of the stroke of the cilia; bivalent and trivalent cation salts with a few exceptions do not. Some acids induce reversal, others do not.2The duration of reversed action varies with the kind of salt and with the concentration. As the concentration increases, the duration of reversed action increases to a maximum and then decreases to zero.3Bivalent and trivalent cation salts neutralize the effect of monovalent cation salts. The relative amount required varies with the kind of salt used and with the concentration.4The amount of a given salt required to neutralize another salt is not proportional to the concentration of the salt neutralized. Weber's law does not hold.5The results seem to indicate that ciliary reversal is associated with differential adsorption and consequent changes in electric potential, but that there are also other factors involved.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 43 (1926), S. 119-145 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The chromosome number in the domestic fowl is approximately thirty-five or thirty-six. It is difficult to determine the exact number, owing to the smallness of the shortest chromosomes of the complex and also to the tendency of the chromomeres to occasionally appear as discrete chromosomes rather than as parts of a whole.Difficulty experienced in fixing adult testes has prevented a satisfactory demonstration of all stages of spermatogenesis. However, satisfactorily preserved prophases of first spermatocytes have been observed which, together with the large amount of embryonic material available, have made it possible to work out the behavior of the sex-associated chromosomes with reasonable certainty. Measurements of the chromosomes indicate that the longest chromosome in the cell is single in the female and paired in the male. Two classes of eggs are therefore possible - one with and one without this long chromosome, while all the spermatozoa produced are alike in possessing the long chromatic element. The female is therefore heterozygous and the male homozygous in regard to this chromosome which affords a cytological parallel for the genetic evidence of the heterozygosity of the female.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 43 (1927) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 9
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 43 (1926), S. 147-179 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Animal posture cannot be regarded as an actual inheritance, for it constitutes a current physiological interaction between gravity and an organism, according to the structure and physical powers of the latter. Hence, ‘inherited posture’ merely implies that in a given species physical qualifications are congenitally transmitted, which facilitate a certain characteristic position of the body. Evolution of posture, therefore, has inevitably been associated with corresponding evolutionary changes in organic structures.Evidence furnished by the application of biomechanics to studies of ancient and modern primate structures indicates that man's erectly supported body posture could only have originated from a vertically suspended posture (arboreal).The fact that the prehuman stem passed through an earlier arboreal and brachiating period is attested to by the grasping character of his hands, the ratio of arm-body length, the extreme mobility of the shoulder-joints, as well as the extension of his legs on the body.The semierect posture of the great apes is not an advance toward human bipedism, but a modern reversion toward quadrupedism.Postural evidence conforms with the many other lines of testimony which maintain the close relationship of the human and anthropoid stems, and signifies that man has been an erect terrestrial biped since the time of his physical origin.
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  • 10
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 43 (1927), S. 267-297 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: All phases of mitosis have been observed in the ciliated cells of the pharynx and esophagus of the tadpole of the green frog, Rana clamitans. Centrosomes have been observed in ciliated cells. These data contravene the hypothesis of Lenhossék and Henneguy to the effect that ciliated cells cannot divide by mitosis because they have lost their centrosomes in the formation of the basal corpuscles to which the cilia are connected, and the corollary to this hypothesis (Jordan, '13), that in consequence ciliated cells must divide by amitosis. From counts of cells with cilia, those without cilia but with basal corpuscles, and those without either cilia or basal corpuscles in different phases of mitosis, it is inferred that the cilia are lost during mitosis.Cilia sprout from basal corpuscles, and not from mitochondria in cells undergoing ciliogenesis. From the presence of diplosomes in the distal region of cells in which basal corpuscles are developing, it is assumed that the basal corpuscles arise by partition of the centrosome of the preciliated cell. The centrosome, however, does not become completely lost by reason of this process, but retains enough vitality to insure mitosis. Amitosis, which occurs in some of the ciliated cells, results, according to these data, from degree of differentiation, not from structural deficiency.
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  • 11
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 43 (1927), S. 299-345 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The chondriosomes are first recognizable as two clusters in contact with the nuclear wall. Beneath each cluster lies a chromosome. This relationship is constant and indicates that these two chromosomes play a part in the growth and development of the chondriosomes. The two masses fuse and the single mass grows considerably during the early growth period. Later it breaks up into a number of threads which become rings in the late growth period. The rings fuse into the large nebenkern which plays the usual rôle in the formation of the tail.The Golgi material is first seen outside of the chondriosomal cap. Early in the growth period, it breaks up into Golgi bodies which remain distributed in the cytoplasm during the growth period and spermatocyte divisions. About the midgrowth period a large number of spheres suddenly arise. Since they later fuse to form the idiosome, they are called the proidiosomal spheres. These spheres, which may originate in the Golgi bodies, remain scattered in the cytoplasm during the growth period and spermatocyte divisions. In the spermatid the Golgi bodies collect about the idiosome to form the acroblast. The Golgi remnants pass into the cytoplasm of the tail, while the acrosome elongates into a tail-like structure at the anterior end.The centriole was followed with unbroken continuity from the midgrowth period into the middle-piece of the sperm.
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  • 12
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 43 (1927), S. 347-385 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development of the thigh musculature in a series of chick embryos is described and figured. In the earliest the muscular tissue is in the form of two distinct masses lying on opposite surfaces of the limb. Later, both divide into proximal and distal portions at the knee. The proximal portions, by a series of divisions, gradually attain the condition found in the adult thigh.The embryological findings tend to support the theory of the derivation of tetrapod limb musculature from the two opposed (dorsal and ventral) muscle masses of the paired fins of bony fish.The reptilian homologies of the ilio-trochanterici cannot be definitely ascertained from embryological evidence.The ischio-femoralis (= ischio-trochantericus), Previously regarded as dorsal, and the coccygeo-femorales, previously classed as incertae sedis, are in reality members of the ventral group.The distinction between ‘intrinsic’ and ‘extrinsic’ muscles inserting on the free limb appears to have no embryological or phylogenetic basis in fact.Double innervation (motor) is a primitive condition in tetrapods.Rotation of the avian pubis is correlated with an improved functioning of the obturator in the rotated position coupled with a lack of interference with the other musculature concerned.
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  • 13
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 44 (1927) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 14
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 44 (1927), S. 1-20 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ant Formica exsectoides F. builds mounds with some reference to sunlight, and measurements of internal temperatures have shown them higher in upper parts of the mound, but different in different faces of the mound - all higher than the earth outside the mound.Inside temperatures are not constant; they are due to the sunshine. The mound is so fabricated that the internal temperatures are conserved during the night. The ants make use of the differential internal temperatures for rearing broods.Some mounds show bilateral symmetry dependent upon sun exposure.Measurements of rate of running of these ants show a falling off with lower temperatures, and possibly this is one factor in the smaller development of northerly aspects of these mounds.
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  • 15
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 44 (1927), S. 21-28 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Experiments designed to ascertain the effect of hydrogen-ion concentration on encystment in Didinium were carried out by depriving didinia of food in mixtures of spring water and buffer solutions whose hydrogen-ion concentrations varied from pH 5.0 to pH 9.6, and by counting the number of didinia which encysted and the number which remained active and ultimately died of starvation.The maximum percentage of encystment was attained between pH 6.4 and 8.4, the range in hydrogen-ion concentration which is also most favorable for the growth of didinia; within this range the encystment rate was practically constant and was about 52 per cent. The solutions having hydrogen-ion concentrations between pH 6.4 and 5.0, the acid death limit of the race of Didinium used in the experiments, and between pH 8.4 and 9.6, the alkaline death limit, inhibited encystment, the more injurious solutions producing the greater decrease in encystment rate.The results indicate that the limits of hydrogen-ion concentration within which Didinium can live are practically the same as those found by Crane for Paramecium (approximately pH 5.0 to pH 9.6). They indicate further that concentrations of hydrogen ions which are unfavorable for the growth of didinia do not facilitate encystment and, in general, that changes in hydrogen-ion concentration are of little importance in inducing encystment in Didinium.
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  • 16
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the ovary of the rat the ova arise by proliferations from the germinal epithelium, all cells of which are potential ova. This proliferation begins with the differentiation of the gonad, and may last as long as 369 days postpartum. The embryonic ovary is filled with ova which pass through the typical maturation phases. This continues until five days after parturition. These ova degenerate, none being found in the ovary of the twenty-day rat. After the fifth day postpartum, nuclear development in the ova changes until, by the twentieth day, no typical maturation phases are present. With the degeneration of the embryonic ova the ovary takes on the adult structure.The ovary of the adult female rat shows a modified type of meiosis in the germ cells, while that of the embryo shows the typical phases, indicating that this is the primitive type, with the modified form an acquired characteristic.Ova in a single rat may show both twenty-one and thirty-one chromosomes.Follicle cells are formed from the cells of the germinal epithelium and, like the sex cells, may have both forty-two and sixty-two chromosomes in a single follicle. The lutein cells also show both forty-two and sixty-two chromosomes in a single corpus luteum. The chromosomes of the lutein cells enlarge with the expansion of the cell to a size greatly in excess of the chromosomes of the somatic cells. The theca interna is derived from the tunica albuginea.
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  • 17
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 48 (1929), S. 585-609 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The caeca of fourteen bantam fowls have been studied. These fowls ranged in age from six days' incubation to three years after hatching. Between the fifth and sixth days of incubation rectal caeca arise as evaginations from the intestine at the junction of the ileum with the colon. The develoing caeca closely resemble histologically the intestine to which they are attached.The caeca are essentially devoid of content until about the nineteenth day of incubation, but during the remaining days of incubation are gorged with a bluish-gray material similar to that found in the colon. Thus, an early defecatory function is indicated.In general, the proximal third of the caeca remains histologically similar to the intestine, but the distal two-thirds undergoes regression. The latter involves the atrophy of the epithelium and glands, accompanied by the appearance of lymphoid tissue. Much of the lymphoid tissue eventually disappears, to a large extent by atrophy and dissolution of the leukocytes. However, to some extent, lymphocytes develop into granulocytes which escape with other leukocytes into the lumina of the caeca and there disintegrate.Lymph nodules begin to appear in the caeca about one week after the chick hatches. The leukocytes, at least in part, arise in situ from the reticular stroma. Eosinophils arise in certain areas of the tunica propria, and in the earlier stages of their development resemble large lymphocytes, in the cytoplasm of which basophilic, amphophilic, and acidophilic granules are intermingled.
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  • 18
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 43 (1926) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 19
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The integument of the vermilion-spotted newt contains three kinds of pigment--yellow, red, and black. The yellow is uniform and continuous over the whole body; the red and black are discrete, and are chiefly in large spots. The pattern does not change measurably in an adult individual.Functional changes in contraction of the scattered dorsal melanophores were uncommon. The only efficient single factors found were a long subjection to low temperature (expansion) and injection of pituitrin (contraction).Removal of skin was followed by a rapid mass migration of dermal elements into the wound area. Melanophores were thus furnished to a dorsal wound, and after several months black spots formed from these. Red pigment never regenerated nor migrated into a wound. Yellow pigment was formed in situ after the wound had completely healed.Auto-, homo-, and heterotransplants lost their pigment patterns and were gradually reorganized so as to conform in gross appearance to the surrounding pattern of the individual host's skin. The transformation was never complete in eight months, but new black spots and new yellow pigment eventually formed.The behavior of melanophores during morphogenesis differed for specific areas of the integument. Their movements and aggregation were highly coordinated among themselves.
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  • 20
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 48 (1929) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 21
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    Journal of Morphology 48 (1929), S. 281-316 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The arterial system of Uromastix hardwickii retains many primitive features and shows great resemblance and relationship to that of Sphenodon. The heart is typically reptilian. Two systemics and a pulmonary arch arise from the ventricle. The conus arteriosus is absent. The carotids arise together from the right systemic by means of a small common carotis primaria. A very well-developed ductus caroticus connects each carotid with the systemic arch of its side. The ductus arteriosus (ductus Botalli) is absent.The dorsal aorta is formed by the union of both the systemic arches. The left systemic joins entire while the right one, which is termed systemicocarotid trunk, gives off the carotids, the vertebral, a single subclavian, and two pairs of parietal arteries, before the union. Anterior epigastric arteries are altogether absent. The dorsal aorta gives off fifteen pairs of parietal arteries which are segmentally arranged. All the main branches supplying the alimentary canal and other viscerala organs arise independently of one another, there being no such combination as is found in Varanus.
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  • 22
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    Journal of Morphology 43 (1927), S. 181-265 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Contains a description of the very involved process of synapsis, which is displayed with unusual clearness in Mecostethus. It is found that the homologous spermatogonial chromosomes, already longitudinally split in the telophase, become closely associated while still in the diatene condition. From the proximal end of each pair, which attaches to the karyotheca, there spins out a delicate thread. Meanwhile the distal, heavy portion of the spiral, double rod executes a loop so that the proximal and distal ends lie near together. Gradually the remaining heavy portion becomes extended until the entire tetrad is in the leptotene condition. In different species of Orthoptera there are variations in the time of association of homologues. The bearing of the facts disclosed in Mecostethus upon the physical characteristics of chromosomes, their movements and changes in meiosis, their individuality and relation to genetical processes are discussed.
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  • 23
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In Termopsis nevadensis only soldiers are produced during the first three or four years. When a normal colony comprises approximately twenty inhabitants, the first adult soldier is probably in the fifth instar; the second, somewhat larger, certainly is in the sixth. Later, others are produced in the seventh, and after the reproductive caste becomes differentiated, with about 450 inhabitants, they are in the eighth. Finally, in very old communities, some, at least, are in the ninth. The winged insect invariably is in the eighth.No sign of wings exists until the reproductive caste appears, after which every member of the sixth, and probably the fifth, instar possesses small, yet distinct, wing rudiments. These persist and enlarge in the later stages of the reproductive caste, and, of smaller size, they frequently occur in the soldier nymph and to a less degree in the adult. The third-form adult is probably a sexually mature soldier nymph; the second-form adult seemingly has the same origin and, though possessing wing buds, it does not belong to a special caste.Measurements of scores of recently hatched young disclose no differences other than those of ordinary variation, either in width of head, number of antennal segments, or size of brain and gonad. The first visible signs of caste differentiation appear at a relatively late stage. All of the instars are described in detail and the later ones are compared.
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  • 24
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    Journal of Morphology 43 (1927), S. 427-497 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The primordial germ cells are derived from entodermal giant cells which are found first before the gut is formed and later along the ventral and lateral margins of the gut. Some of these cells pass through the lateral mesoderm to a position dorsal to the gut, where they are distinctly recognizable as germ cells. They are then shifted to the gonad region.Sex could be distinguished first at fifty-two days. The female sex is indicated by early maturation stages and the beginning of the oviducal groove. The male sex is distinguished by the presence of the sperm duct. No tendency toward juvenile hermaphroditism is apparent.A portion of the oocytes formed during the first season matures for the first spawning, which takes place at the age of two years. The remainder form a reserve supply, which is increased each year by oocytes formed from dormant oogonia.Maturation in the male begins in September and continues until spawning-time in April. Spermatogonia lying dormant within the cysts during maturation give rise to the sperm of the next season.‘Spermatid masses,’ probably formed by the fusion of spermatids, are found in the cysts with the ripening sperm.Definitive sex cells in both sexes have their origin only in primordial germ cells. No transition from somatic cells to germ cells was found at any stage.
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  • 25
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    Journal of Morphology 43 (1927), S. 521-546 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The literature on the general subject of freezing and survival both in plants and in animals is briefly reviewed and a bibliography given. Insects representing three ecological groups, (1) the oak borers - exposed to temperature extremes normally; (2) stored-products insects representing supposedly a tropical or subtropical group, and, (3) aquatic insects never exposed to temperatures lower than 0°C., were chosen for this study. Determinations of the freezing and undercooling points were made during the yearly cycle.Both the stored-products insects and the aquatic insects studied showed no periodicity in freezing or undercooling. The oak borers showed marked periodicity. The freezing-point varies directly with the moisture content. Cold-hardiness was produced experimentally by, (1) exposure of insects to low temperatures and, (2) by dehydration. Loss of cold-hardiness was produced experimentally by combinations of high temperature, food, and high relative humidity. The freezing-point ordinarily found corresponds with that of the blood. Repeated freezings of the same insect or tissue showed no hysteresis. There exists in certain insects a secondary freezing-point below that ordinarily found. Oak borers in summer condition die at the first freezing-point; in fully hardened condition they die at the secondary freezingpoint.
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  • 26
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The results of the study of certain factors which affect encystment in Didinium nasutum indicate the following: Absence of food constitutes an adverse environmental condition which induces encystment in approximately 50 per cent of the didinia subjected to it, though the presence of a certain amount of food in the cell body is requisite for encystment. The prevention of encystment for 750 generations does not affect the percentage of didinia which encyst in the absence of food, and hence Didinium does not become progressively more disposed to encystment as generations pass. Conjugation does not affect the percentage of didinia which encyst in the absence of food. Metabolic by-products of Paramecium inhibit encystment to a striking degree when didinia are deprived of food in the presence of these products. Metabolic waste of Didinium markedly facilitates its encystment in the absence of food. Hay-infusion culture fluids of different ages have singularly diverse effects on the encystment of didinia in the absence of food; recently prepared infusions inhibit encystment; infusions four to six days old induce encystment in 90 to 100 per cent of the specimens, and infusions seven to fourteen days old, in approximately half of the specimens.
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  • 27
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    Journal of Morphology 43 (1927), S. 547-555 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The diploid number of chromosomes obtained from counts of anaphases of the first somatic mitosis is found to be forty-four. Of these, seven have terminal, thirty-seven non-terminal attachment, giving a distribution of seven rods, thirteen V's, and twenty-four J's. The number is constant in all the fertilized eggs counted, indicating an XX-XY arrangement of the sex chromosomes.
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  • 28
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A histological study has been made of a series of Phrynosoma testes taken at frequent intervals throughout the year. As it was important to differentiate between the amount of interstitial tissue and the number of cells, it was necessary to take into account the percentage of tissue, total testis volume and the number of cells per unit volume.The results show a definite interstitial-cell cycle. Volume of interstitial tissue and size of individual cells are greatest during the breeding season, but the interstitial-cell number is then minimal. The maximal number of interstitial cells occurs after the close of the breeding season. There is, apparently, no reversion of interstitial cells to a connective-tissue-cell type.The above changes are correlated with the spermatogenetic cycle and with increases in total tubule length, in tubule diameter, and in testis volume. The time in which important changes in ovarian volume occur and at which ovulation takes place is coincident with the testicular changes.Interstitial cells have been stated to have no endocrine function for the reason that their number is at a minimum during the breeding season. If, however, interstitial tissue is responsible for sex characters and activity, the present work would indicate that it is the volume of tissue, and not the number of cells, that is important.
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  • 29
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    Journal of Morphology 48 (1929), S. 385-431 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Direction of peristalsis of the dorsal vessel in prepupa, chrysalis, and adult of Lepidoptera is not constantly forward; phases of forward peristalsis alternate with phases either of backward peristalsis throughout the whole dorsal vessel or of diverging waves originating in the third to fourth abdominal segments, proceeding backward and forward. Periodic reversal in the silkworm begins twenty-four hours after spinning, forty-eight before pupation. Pupation occurs during a vigorous backward phase. Soon after pupation, and sometimes during pupation, backward phases consist of diverging waves. Later, and in the adult, complete reversal intermittently occurs. Backward phases in the pupa are long (e.g., fifteen minutes), the average rate slow and variable, quickening at eight to ten days to that of the adult. Any long backward phase shows a gradual slowing down, except approaching pupation when the pulse quickens to equal that of forward beating. Average rate of forward beating is constant at constant temperature, but absolute rate in a long phase gradually slackens. Pauses (sometimes one and one-half hours long in older pupae) often follow forward phases. Alternating phases in the adult, compared with the pupa, are short, about one minute and usually less than one hundred beats. In old moths the phases become still shorter, often being reduced to single beats. Opposing waves occasionally conflict. Periodic reversal occurs for hours after excision of the dorsal wall with the pericardium and heart. As in ascidians, back pressure cannot explain reversal.
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  • 30
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    Journal of Morphology 44 (1927), S. 29-87 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The anlage of the abducens musculature appears first at 24-25 somites as a condensation situated dorsal to the mandibular arch.The anlage of the superior oblique grows forward from a mesodermal condensation situated in the maxillomandibular region, termed for convenience the maxillomandibular condensation. This last consists of three parts: (1) the anlage of the superior oblique: (2) the anlage of the abducens musculature, and, (3) an intermediate region.The intermediate portion of the maxillomandibular mass forms a condensation with which the anlage of the abducens musculature fuses. Its fate is, therefore, similar to that of the so-called ‘muscle E’ of elasmobranchs, which has been described as fusing with the lateral rectus. How much muscle is formed from the intermediate condensation in the chick has not been determined.The development of the pyramidalis and quadratus nictitans muscles, derivatives of the abducens complex, is described.The premandibular head cavities are replaced by solid mesodermal condensations, on the surface of which the anlagen of the oculomotor muscles appear. The premandibular mass expands laterally and anteriorly over the bulbus, carrying the oculomotor muscles to their respective positions on the bulbus.Portions of the premandibular and maxillomandibular condensations not involved in eye-muscle formation take part in the formation of choroid and sclera.The growth shiftings of the eye muscles are analyzed. The order of their appearance is commented upon.
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  • 31
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    Journal of Morphology 48 (1929), S. 543-561 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The parietal fossa or pit is situated in the middorsal line between the ear capsules. From its floor four (sometimes only two) apertures lead into the ear capsules. The anterior apertures are the foramina of the endolymphatic ducts; the posterior ones are the fenestrae. Through the fossa each endolymphatic duct passes from its formen to its external aperture in the dorsal integument, describing in its course a loop with the convexity directed anteriorly. The part of the duct involving the loop is enlarged into an endolymphatic pouch. Into the angle of this loop a small muscle is inserted which is a continuation of the anterior trunk muscles, or one taking a more lateral origin from the edge of the fossa. The fenestra may or may not be closed by a definite fenestral membrane. The posterior semicircular canal (posterior utriculus) bears a peculiar relation to the fenestra. The endolymphatic pouch, like the sacculus, contains otoconia, and sometimes siliceous sand grains. Various functions have been assigned to the endolymphatic organ. There is no convincing experimental evidence as to its significance.
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  • 32
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    Journal of Morphology 44 (1927), S. 89-115 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The investigation is based upon hemal nodes of dog, man, and sheep. The material can be arranged in a regressive series leading from a typical lymph node, except for the occurrence of blood in parenchyma and sinuses, to a lymphoid structure at a late stage of involution. These structures uniformly lack lymphatics. There is no evidence of direct luminal connection between the blood-vascular supply and the sinuses. The observation that certain cervical and subcutaneous lymph nodes of the rabbit undergo a myeloid metaplasia following atrophy and disjunction of their lymphatics is used as an explanatory key of hemal nodes. According to our view, hemal nodes represent stages in the involution of transient lymph nodes. Disjunction of the lymphatics leaves the sinuses filled with entrapped lymphocytes. These differentiate into erythrocytes. These red blood cells may disintegrate and pass into solution or be removed either by giant cells or mononuclear phagocytes. Late stages in this process are represented by small irregular masses of lymphocytes, with wide sinuses practically free of blood.
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  • 33
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    Journal of Morphology 44 (1927), S. 217-264 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A description is given of the cytoplasmic alterations in the ovarian egg of Limulus polyphemus leading to the formation of yolk. The nucleolus is found to arise by the confluence of substance which passes from the cytosome into the nucleus, and it is suggested that the chondriosomes, and possibly also the dictyosomes, are derived from an excess of this substance which accumulates in the cytosome. Chondriosomes and dictyosomes are not present in the oogonia, but appear first in oocytes after the formation of the nucleolus is completed.During oogenesis the nucleolus is very active and the greater part of its substance is passed back to the cytosome. By the application of the method of Bell and Doisy for the determination of phosphate in body fluids, the nucleolus is found to be richer in phosphorus than are the other constituents of the cell. The nucleolar emissions effect the transport of phosphorus from the nucleus to the cytosome, where it is used in the synthesis of yolk. The definitive yolk arises by the interaction of nucleolar emissions, chondriosomes, dictyosomes, and ground cytoplasm.
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  • 34
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Each step forward in the evolution of new organs or new abilities has made possible further evolution, but at the same time has set up mechanical and physiological conditions that place definite limits on the future possibilities of evolution. The exoskeleton has made possible very definite advances in the evolution of insects, but at the same time has limited their evolution in fully as many other ways.Opportunities in evolution opened up by an exoskeleton are its use as armor, as a skeleton, in the development of wings, as protection against desiccation. It has conditioned small size opening up numerous limited environments, increasing mutability due to short life. It conditions a tracheal system which speeds metabolism, and a variety of specialized mouth parts as well as locating the sense of smell on the surface where it is more effective. Metamorphosis evolved from ecdysis.Limitations imposed by an exoskeleton are small size, simple nervous system due to small size, short life preventing education, inflexible societies due to simple nervous system, cold-bloodedness, clumsy appendages, loss of closed blood system, excretory system reduced to malpighian tubules, poor development of touch and hearing and mosaic vision.
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  • 35
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    Journal of Morphology 44 (1927), S. 313-339 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The rates of oxygen consumption of single pupae of blowflies (Phormia terraenovae, Phormia regina, Lucilia sericata), of the flesh fly (Sarcophaga sarracenioides Aldrich), of the Mediterranean flour moth (Ephestia kuehniella), and of the bee moth (Galleria mellonella) during metamorphosis, until emergence, have been determined. The record for each pupa, with the exception of those of blowflies, is practically continuous day and night during the period of pupal development which lasted from 140 to 300 hours, according to the species, at the temperatures used. During pupal development there is first a period of decrease in rate, which is later followed by a steady increase until a short time before emergence, when a sudden decrease occurs.The ‘oxygen curves’ of the blowfly pupae (Diptera) are quite different from those of the flour-moth and bee-moth pupae (Lepidoptera), although all are of the same general U-shaped type. There are strong indications of a specific difference in the curves of the blow-fly pupae. The flour-moth pupae curves differ slightly from those of the bee-moth pupae. During the major part of development the rates of O2 consumption of pupae of both sexes of bee moth and flour moth are about the same, but near the end of metamorphosis the females have higher rates than the males. No such sex difference appears among the dipterous pupae used.
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  • 36
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    Journal of Morphology 44 (1927), S. 341-361 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Conjugating individuals of Metopus sigmoides fuse at the anterior end, the pair presenting the appearance of an inverted letter U. The micronucleus of each conjugant by two successive divisions forms four micronuclei. Three of each four degenerate and the fourth by division forms the pronuclei. Cytoplasm and pronuclei from one conjugant pass over into the other, leaving the old macronucleus and a minimum of cytoplasm behind in the shrunken pellicle of the smaller conjugant, which then separates from the larger one. In the larger exconjugant two pronuclei fuse, forming the functional synkaryon; the two residual pronuclei degenerate and disappear. The synkaryon divides. One of the daughter nuclei condenses into the new micronucleus, the other grows into the new macronucleus. The old macronucleus liquefies and is absorbed. The larger exconjugant, after losing its cilia, secretes a cyst wall about itself and becomes dormant. The whole process requires at least six days for its consummation.
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  • 37
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    Journal of Morphology 44 (1927), S. 363-372 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The history of investigations on the contractile vacuole is reviewed briefly and brought up to date.The study of the contractile vacuole in Amoeba proteus is considered from standpoints of origin, structure, behavior, and function. The results are obtained from a prolonged study of normal organisms and from their reactions when introduced into conductivity water.The origin of vacuoles is studied by means of dark-field illumination which reveals the vacuole to be formed from a fusion and coalescence of extremely minute droplets.The retaining ‘wall’ of the contractile vacuole is not a permanent structure, but is in the nature of a condensation membrane, totally disappearing with each contraction.The loci of the contractile vacuoles are not permanent, but vacuoles are formed more or less at random. It is unlikely that they are supported in gelated areas, for amoebae with a dozen vacuoles are quite active and there is no interference with amoeboid movement.Conductivity water increases the size, number, and rate of contraction of contractile vacuoles, which suggests that they may function in maintaining an osmotic gradient as well as in the elimination of metabolic waste.
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  • 38
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    Journal of Morphology 45 (1928), S. 1-45 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Five characters-flatness, elongation, posterior pointedness, delay in division of the body, delay in completion of mitosis-are so distributed among the subdivisions of the Opalinidae as to involve either repeated fortuitous appearances of these characters, a thing not to be believed, or trends resident in the germ plasm. The Ophryoscolecidae show similar distribution of two sets of characters. In the Salpidae there is evidence of trends toward: coiling of the gut; decrease in number, size, regularity, and symmetry of body muscles; simplification and degeneration of the eyes. These qualities appear first in the phylogeny in the chain Salpas, the final phase in the life-cycle. In the course of the evolution the solitary Salpas become more and more modified in the same directions, until, in the most highly modified species, the muscles and eyes are as much modified in the solitary Salpas as in the aggregated. These changes, not disadvantageous but rather adaptive in their beginning in the colonial individuals, are harmful to the solitary Salpas, yet the degeneration is, by precocious development, thrown back onto the earlier phase of the life-cycle, the solitary stage. Precocious development is not purely utilitarian, but may be more fundamental, biological.Evolution is discussed in terms of trends resident in the germ plasm, their origin in connection with mutations, their growth, decrease, disappearance, branching; auto-evolution. Discussion is from the standpoint of the germinal stream, internal factors of evolution being emphasized.
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  • 39
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A chronological investigation of the histological condition of the right ovary of the domestic hen from embryos of nine days' incubation to adults of eighteen months was made. A rudiment of the right ovary is found at all times. Its composition is variable. Sixty-one per cent of the rudimentary ovaries contained medullary tissue only. Thirty-nine per cent had rudiments of cortex, in addition. The occurrence of cortical rudiments in embryonic stages is the probable basis of ovarian follicles found in the rudimentary right ovaries of adults. Primordial germ cells persist in the medullary tissue until three weeks after hatching. They subsequently appear to atrophy. The medullary cords persist through the entire period either as distended tubules or as solid cords of modified epithelial cells. Remnants of the right mesonephros persist as tubules and connect with the gonad by rete tubules. The mesonephric duct maintains a patent lumen.
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  • 40
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Virulent hay-infusion cultures of Bacillus pyocyaneus are toxic to pure-line races of three species of paramecia, but these races may acquire a tolerance for this toxic agent. Races with acquired tolerance have been grown for long periods of time in toxic, pure cultures of B. pyocyaneus by means of the daily-isolation culture method, and here the average division rate is as high as, or higher than, in the chance-mixed bacterial cultures in which these protozoa are usually maintained in the laboratory. The tolerance is lost, however, when the paramecia are removed from the toxic cultures and grown for a number of generations in cultures of non-toxic bacteria.The toxic agent that is lethal to paramecía is probably the soluble toxin of B. pyocyaneus. The investigation shows that the agent is soluble and either thermolabile or volatile. It also shows that all deleterious substances, other than the soluble toxin, known to be produced in cultures of this bacillus, are non-lethal to paramecia.Hay-infusion cultures of Bacillus enteritidis were lethal to paramecia. All attempts to develop tolerance in paramecia for the toxic agent in these cultures failed.Under the experimental conditions that prevailed, diphtheria toxin was found to have no appreciable effect upon the division rate or death rate in three species of paramecia.
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  • 41
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Fetuses from forty-three gravid uteruses from sows of known breeding dates, as well as from 448 uteruses with unknown breeding dates, were studied. Growth curves are given for weight and length of fetus and for weight of fetal membranes. The weight of the fetus first reaches that of the fetal membranes between the sixtieth and seventieth days of pregnancy. Degenerate fetuses were found in 3.68 per cent of the cases. They were found at all stages of gestation. Size of litter was found to decrease from 11.4 at the twentieth day to 6.8 at the 110th day. Also, the calculated per cent of ova lost up to each ten-day stage tends to increase as gestation advances. Crowding was found to be an important factor, but probably not the only factor, in causing degeneration. Genetic factors were probably responsible for part of the resorbing fetuses.In the study of the normal fetuses, significant correlations were found between fetus length and weight of fetal membranes, as well as between fetus weight and weight of fetal membranes. Lower correlations, but probably significant, were found between total distance (spacing) between fetuses in the uterus and weight of fetal membranes. Correlations between size of fetus and total distance between fetuses were very low. As in the case of the degenerates, crowding has an important relationship to size of fetus, but is probably not the only factor involved.
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  • 42
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The spermatogenesis of five guinea-pigs was studied. The spermatogonial chromosome number is approximately sixty-two plus or minus two. The primary spermatocyte number is approximately thirty-one. The spermatogonial number in the early prophase is lower than it is in later stages. This condition is due to late fragmentation of the large chromosomes found in the earlier stage. A possible sex chromosome of the X-Y type may be identified. Its components segregate during the first maturation division.
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  • 43
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    Journal of Morphology 46 (1928), S. 275-315 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Material of the domestic fowl of appropriate ages, ranging from twelve hours' incubation to the adult bird, was prepared for the purpose of studying the production and development of the germ cells.The primordial germ cells arise in the extra-embryonic region anterior to the head fold in the region of the zone of junction during the primitive-streak stage. These germ cells migrate, through the blood stream, to the region of the future gonad, where they develop into the definitive germ plasm.There is no widespread degeneration of the primordial germ cells after their arrival in the gonadal region, nor is there any widespread transformation of somatic cells into definitive germ cells.
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  • 44
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    Journal of Morphology 47 (1929) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 45
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    Journal of Morphology 47 (1929), S. 335-413 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: An attempt is made to define lips, and on Danforth's interpretation of homology, homologous lips are found at certain stages of development in some representatives of all classes of vertebrates. The primary lips characteristic of selachians, after the maxillary and premaxillary bones have developed within the territory of the upper lip (toadfish, cod), may disappear (trout, Spelerpes), accompanied by a forward migration of the lower jaw. The secondary lips of higher forms are first indicated in certain teleosts and amphibians. Lips vary in structure to accord with their physiological functions, whether sensory, prehensile, or adhesive. Lips of the cod are highly sensory; those of the tadpole and of grazing animals, in different ways, are notably prehensile; the lips of petromyzon and the vampire, having abundant villi, are most effectively adhesive. Therefore, the smaller villi of the lips of suckling animals are presumably for tight adhesion to the nipple. The opossum and rat, however, nurse before their lips have developed. No free macroscopic villi are found on human lips, but there is a zone of thick epithelium tending to form villi. Such a zone is shown to be a widespread feature of vertebrate lips.
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  • 46
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    Journal of Morphology 47 (1929), S. 415-433 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The diploid number of twenty-six chromosomes was found in the mature parthenogenetic female-producing eggs and also in the somatic cells of the female embryos developing from such eggs. In the maturation stages of a few of these eggs the chromosomes were markedly larger than in the corresponding stages of the majority of the eggs. Whether this size difference of the chromosomes is correlated with male- and female-producing individuals has not been determined. The mature parthenogenetic male-producing eggs contain the haploid number of thirteen chromosomes, and this number was found also in the somatic cells of the young male embryos. The mature sexual eggs contain thirteen chromosomes.In spermatogenesis the secondary spermatocyte divisions are usually omitted and the secondary spermatocytes develop directly into the motile spermatozoa containing thirteen chromosomes. A few, however, of the secondary spermatocytes divide, forming spermatids containing fewer than thirteen chromosomes. These cells develop into the non-motile and rudimentary spermatozoa.The motile spermatozoa containing thirteen chromosomes unite with the parthenogenetic male-producing eggs containing thirteen chromosomes, thus producing the fertilized eggs with the diploid number of twenty-six chromosomes. These fertilized eggs develop into female-producing females which reproduce parthenogenetically.
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  • 47
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    Journal of Morphology 47 (1929), S. 519-529 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The liver has a rhythmic function with alternating assimilatory and secretory stages. The height of the assimilatory stage in rabbit's liver is characterized by the following qualities: All the cells are usually expanded and contain much glycogen and few bile components. The bile capillaries are narrow and generally empty. The glycogen content is high (about 13 per cent); the total glycogen weight is also high (about 17 grams). The liver has a relatively heavy weight (about 140 grams), a large volume, notably firm consistency, and a light brown color.The secretory stage at its height has the following characteristics: All cells are shrunken and are rich in bile components, but contain little glycogen. The bile capillaries are expanded and filled with secretion (fixation with barium chloride). The glycogen content is low (about 1 per cent), and the total glycogen weight is also low (about 1/2 gram). Weight of liver low (about 50 grams). Volume small and consistency fairly flaccid. Color dark reddish brown.Between these two extremes are various intermediary stages. Such variations as these probably occur during the normal functioning of the liver in man and also in other animals.
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  • 48
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    Journal of Morphology 48 (1929) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 49
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    Journal of Morphology 47 (1929), S. 555-587 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The germ cells of Lebistes are found in cysts; the younger cysts are toward the cortex. Mitochondria and Golgi apparatus are present. During maturation leptotene, bouquet, pachytene, and diakinesis figures are seen. The spermatocyte chromosomes number twenty-three; an X-Y pair is probably present, though the evidence is not conclusive. In spermatid formation the centriole divides to form a rodlet and an axial filament; the nucleus segregates into two materials, one of which is extruded; the remainder first contracts to a cup, comes in contact with the rodlet, then again forms a sphere. The mitochondria are arranged along the proximal part of the axial filament; the sphere flattens and elongates; the rodlet sinks into the head substance and is enfolded by it. The Golgi remnant is sloughed off with the residual cytoplasm, which disappears at the same time the Sertoli cells show an increase in size, suggesting their ingestion of the spermatid remnants. The mature sperm form spermatozeugmen, which are stored in the testicular canal; they are transferred to the female by aid of the modified anal fin.
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  • 50
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    Journal of Morphology 48 (1929), S. 1-43 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The parenchymal cells in the parathyroids of Rana catesbeiana (Shaw) are found to undergo a very curious cyclic change. The cytoplasm is broken down by a process of cytolysis. The nuclei are decomposed by chromatolysis and pycnosis. The entire parenchyma is finally liquefied, except for a layer of cells lining the capsule.The parathyroid body is reconstructed by young cells which are produced from rather definite growth centers. The process of regeneration begins some time before cytolysis is completed and continues until the entire organ is restored.The cytolytic and regenerative processes transpire in such sequence that the amount of apparently healthy tissue present at any one time is a rather large portion of the total mass normally present.The relationship between the parenchymal tissue and the stroma of the parathyroid is described.
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  • 51
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    Journal of Morphology 48 (1929), S. 563-584 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: From the structure of statocysts, in the so-called phylogenetic tree of the Cephalopoda, the genus Scaeurgus is to be placed on the same branch as Polypus.Meleagroteuthis has the same number of processes as Watasenia, Enoploteuthis, Abralia, Illex, and Stigmatoteuthis, which have ten processes, but in this genus the structure of statocysts seems to be tolerably well developed. For this reason, the author places this genus as a branch between Abralia and Illex.Those three genera - Gonatus, Sthenoteuthis, and Onychoteuthis - which have eleven processes in a statocyst are to be placed in the same branch as Berryteuthis, Gonatopsis, Ommastrephes, Eucleoteuthis, Moroteuthis, and Symplectoteuthis, which have the same number of processes; of these, Gonatus, which has the most primitive structure of the statocyst, is to be put in the lowest position on that branch; but Sthenoteuthis, which has the same structure of the organ as Ommastrephes, is to be placed on the twig near Ommastrephes; and, lastly, Onychoteuthis has the same organ as that of Moroteuthis, which fact induces the author to set this genus in the position nearest to Moroteuthis.The statocyst of Lolliguncula corresponds exactly to that of Loligo, which has twelve processes; this condition puts this genus on the same twig as Loligo.
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  • 52
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    Journal of Morphology 41 (1925), S. 239-265 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper reports experiments with Fundulus heteroclitus to modify larval development by means of ultraviolet radiation. Eggs were exposed to radiation at various intervals after fertilization for varying periods of time. The results accord with previous work on fish teratology, and the developmental types obtained are essentially similar to those produced by chemicals, cold, and hybridization. The deviations from normal development occur in the same body regions as do those in other vertebrates whose early development has been modified by the action of radiation (x-rays, radium, etc.).The results of these experiments indicate that there is a non-specificity in susceptibility relations with the production of similar types of monsters for widely different reagents. That these eggs are differentially susceptible to the action of ultraviolet radiation is indicated by the fact that those regions which have the highest metabolic activity when an inhibiting influence is active are the ones most generally affected. Thus modifications of the nervous system, sense organs, circulatory system, tail region, and body axis result, respectively, in the production of varying degrees of cyclopia, inadequate circulation, short, stubby or bent, non-motile tails (some bifid), and anterior twinning.As these modifications may be produced by applying inhibiting influences during the first few minutes after fertilization, it is evident that there is in the egg at this stage some constitutional or physiological basis which determines early differences in susceptibility of its various parts.
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  • 53
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    Journal of Morphology 41 (1926) 
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  • 54
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    Journal of Morphology 41 (1926), S. 427-439 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Webbing of toes or fingers in man is produced by a local arrest of development, causing retention of the normal embryonic webbing. This type of digital fusion involves only the skin, the skeleton being unaffected. The extensor tendons of the toes may sometimes be fused.Webbed digits occur normally in some marsupials, rodents, and insectivores, in a number of lemurs and catarrhines, and in the siamang and gorilla. They also may occur in varying degree in other Primates, notably Hylobates. An analysis of five new pedigrees together with those already published demonstrates that webbing of toes in man may be inherited in either a mendelian or sex-linked manner. In one case this character follows the course of the Y-chromosome.
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    Journal of Morphology 41 (1926), S. 333-345 
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    Notes: In a leech infesting the Alaskan codfish germinal masses in the ovary proliferate secondary groups, comprising about forty cells in which a follicle and central supporting cell early differentiate. Active division results in approximately 500 cells which apparently develop ductules extending to a point on the surface of the egg. Granules of unknown origin then appear in each nurse cell, and are drawn down the ductules into the egg which can now be distinguished. Reasons are given for the belief that the nutritive material is drained from the nurse cells by amoeboid activity of the egg. In early stages the nutritive mateiral forms a loose reticulum which gradually becomes transformed into a more extensive network, persisting until the maturation divisions. In this latest period the follicle and nurse cells, which become shrunken as the ovum enlarges, usually are stripped off and soon disintegrate.
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  • 56
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    Journal of Morphology 42 (1926), S. 23-81 
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    Notes: The flagellate, Tetramitus rostratus Perty, appeared in cultures of certain amoebae obtained from the coecum of rats. In a typical life-cycle a cyst, planted in an appropriate medium, gives rise to an amoeba which may divide a number of times, but eventually some of the amoebae transform into flagellates identical with Tetramitus rostratus. These divide frequently through several days, sometimes for weeks or months, and then transform back to amoebae which become encysted.During excystment the smooth cyst wall dissolves. Usually both the amoeboid and flagellate phases pass into a “gel” state during division. A “gel” state sometimes occurs during transformation. The time required for transformations varies from a few minutes to several hours.Many culture media and methods have been tested. In certain cultures the flagellate phase was prolonged for weeks or months. These cultures were characterized by: 1) great variation in size, from minute “dwarfs” to oversized “monsters”; 2) frequent multiple fission; 3) pairing and fusion, and, 4) some evidence for the origin of secondary nuclei from chromidia. In cases of pairing and fusion, the process of maturation and union of nuclei could not be definitely proved, although suggested by the observations.The flagellate phase is more probably the “adult” phase because of its complex organization and possible sexual phenomena. This case is considered an extreme for this type amoeba-flagellate transformation.
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    Journal of Morphology 42 (1926), S. 111-141 
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    Notes: Disintegration in killing agents was studied throughout development. In the unfertilized egg and cleavage stages the death gradient runs from animal to vegetal pole. In the late blastula stage the future dorsal surface and future point of gastrulation show heightened susceptibility. The gastrula has a gradient from anterior to posterior end along its dorsal surface, with a slight reverse gradient around the blastopore; lateral and ventral regions are least susceptible.Before and after the appearance of the neural groove, the dorsal surface shows increased susceptibility with gradient in it from anterior to posterior end. The neural tube is highly susceptible, with a death gradient from anterior to posterior end and a slight reverse gradient at its posterior end.During late stages and in the larva the double gradient is present; death begins at the two ends and progresses backward from head, forward from anus; from the former most rapidly. The least susceptible place is near the posterior end. The posterior reverse gradient is less developed in the lamprey than in other vertebrate embryos, due, probably, to its lack of a tail bud.Assuming that death differences indicate differences in rate of activity, it appears that such differences in activity may be causes and not results of developmental processes, for the development of certain parts (dorsal surface, blastopore, central nervous system) is indicated by heightened activity before it is evident morphologically.
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    Journal of Morphology 42 (1926), S. 143-195 
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    Notes: On the basis of experimental study and observations on the morphology of the legs of spiders, P. Friedrich described a cutting device within the trochanter which would sever that appendage from the body when the leg was stimulated by injury.A reinvestigation of the problem yielded entirely contrary results. Experiments calculated to induce spontaneous amputation through an automatic reflex in the leg were negative on scorpions, harvestmen, and more than a dozen species of spiders. A detailed morphological study of the skeleton and musculature of the arachnid leg showed that no autotomizing device exists, either in the skeleton or in the arrangement of muscles (as is usually supposed). In all species studied, except the scorpion, severance of the leg from the body occurs most readily at some given point. The point at which severance readily occurs is directly correlated with a definite structural weakness in the skeleton and musculature. The spider itself removes an injured leg by grasping the stump with its mouth-parts. No such injured stump falls off spontaneously or without the application of tension. Scorpions do not autotomize appendages under any stimulation, nor do they show any anatomical weakness in the leg skeleton or musculature.Autotomy as an automatic reflex does not exist in the Arachnida.
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    Notes: The claspers of Centrina are adnate with the pelvic fin and bear a spine as in other Spinacidae. Mustelus canis resembles M. lunulatus rather than M. vulgaris. The claspers of Chiloscyllium end in a pointed spike. Pseudotriakis resembles the Carchariidae. The three North American Atlantic species of the genus Raia are considered, and R. laevis and R. erinacea are placed in the pseudogenus containing R. batis, and a new pseudogenus erected for R. ocellata. A gross and histological account is given of the Cowper's glands of Homo, and they are shown to be homoplastic with clasper glands, similar in structure, arrangement, development, and function.
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    Journal of Morphology 42 (1926), S. 453-471 
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    Notes: The activities of the larva and the responses and orientations it makes to external stimulation, and the structural organization by which these activities are produced, are described and figured.Existing systematic confusion of M. citrina with other species (M. manhattensis, M. nana, and M. microsiphonica) is cleared. The duration of the period of larval life is found to vary between 5 and 170 minutes. A proportionally small number retain the larval form a longer time. During larval life, periods of swimming movements alternate with periods of inactivity, the latter, at first of momentary duration, becoming longer and longer until activity ceases.No light receptor exists and no response to light is made. A statolith is found in the sensory vesicle, and frequent geonegative orientations are made during the free-swimming period. These are of short duration and tend to occur, 1) when it emerges from the parent; 2) at the beginning of each of the frequently recurring periods of swimming activity; 3) immediately upon making contacts. Unoriented movements follow each orientation and constitute much the greater part of behavior.The larva lacks definite organs of attachment. The entire surface of the tunic becomes adhesive at the time of metamorphosis. Only those structures that make up the action systems of the larva are fully differentiated, all other parts are embryonic in condition.
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    Journal of Morphology 44 (1927), S. 127-216 
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    Notes: This study represents the first critical investigation on the development of the embryonic skull of the porcupine. A complete series of stages makes it possible to trace the developing chondrocranium from its first formation in precartilage to its later transformation into cartilage bone. Concurrent with this growth is the investment of the cartilaginous cranium by membrane bone.The very primitive nature of the chondrocranium offers an excellent opportunity to discuss the existing problems of the embryonic skull from a new angle. Evidence is presented in support of the assumption that the ala temporalis is the homologue of the cynodont epipterygoid. The lamina parietalis develops from a single chondrifying center, thus producing a different arrangement of parietal elements from that found in most mammals. New evidence as to the relationship of the dens epistrophei and basal plate is presented. The position of the internal carotid artery on entering the cranium is different from the condition found in most mammals and throws new light on the interpretation of surrounding structures. The presence of a structure comparable with the crista longitudinalis of Lacerta shows close affinity to the solum nasi of more primitive forms.The great specialization of the face is seen in the early and rapid growth of the membrane bones. The chondrocranium is long persistent and cartilage bone appears late in embryonic life.
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    Notes: In conjugation fusion occurs along the entire oral surfaces of the proboscides of Dileptus gigas. Two size-reducing divisions occur in rapid succession immediately preceding conjugation. Only one of the many micronuclei takes part in the process of nuclear reorganization. All other chromatic material is massed at this time in the posterior portions of the conjugants. The pronuclei are derived from the single active micronucleus, and interchange occurs immediately preceding the separation of the mating individuals. The fertilization nucleus divides to form two nuclei of diverse size. The smaller one produces thirty-two or sixty-four micronuclei, while the larger one divides to produce a like number of macronuclei, each of which finally breaks up into many chromatic granules which form the numerous densely staining nuclear derivatives which are characteristic of the vegetative stage of Dileptus gigas.In the early stages of this reorganization process specimens are frequently found with from two to eight distinct nuclei often arranged in a series as in a beaded nucleus. This condition probably explains the frequent references in literature regarding such a nuclear condition in Dileptus.Dileptus gigas has, accordingly, in the vegetative stage, a multinucleate condition with reference to the micronucleus and a fragmented or distributed condition with reference to the macronucleus.
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    Journal of Morphology 44 (1927), S. i 
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    Journal of Morphology 45 (1928) 
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    Journal of Morphology 45 (1928), S. 187-207 
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    Notes: This paper deals with the description of an organism, externally resembling Müller's larva among the polyclads, collected in the plankton of Monterey Bay, California, during the spring and summer months. Internally, the organization of the various systems is unique. In some respects it bears a certain resemblance to a polyclad in early stages of development; in other regards it approaches the rhabdoceles, more particularly the Acoela. Its more exact relationships are obscured by the fact that, although the larger specimens are not more than 0.7 mm. in length, the sex organs, both male and female, are fully developed and functional. Furthermore, the plan of these systems is unlike that of any turbellarian hitherto described. Whether this organism represents a case of paedogenesis or is a fully developed adult is unknown at present, but in any event the various systems are described and an attempt is made to give it a fairly definite systematic position.
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    Journal of Morphology 45 (1928), S. 209-231 
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    Notes: The highly specialized cranial musculature of the toadfish is characterized by the following features: 1Absence of intermandibularis and branchiomandibularis muscles.2Presence of levator premaxillaris muscle.3Very large branchial chamber, the outer wall of which is formed by seven branchiostegal rays connected by a strong fascia provided with muscles (oblique levators and adductors).4Highly developed masticator muscles (adductor mandibularis and pterygoids).5The rectus abdominis, sternohyoid, and hyohyoid muscles are attached by a median aponeurosis to the hyoid and basibranchial elements and directly to the hypobranchial cartilages; this muscle complex depresses the buccal floor in opposition to the geniohyoid.6The pelvic fins are in the jugular position.7Two narrow muscles connect the cleithrum with the fourth ceratobranchial.8The cranial musculature is obviously adapted to a carnivorous habit and particularly for increasing respiratory capacity under asphyxial conditions.
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    Journal of Morphology 45 (1928), S. 233-257 
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    Notes: The cytological and histochemical evidence presented in this paper shows the following facts: (1) The mitochondria are not directly transformed into yolk. They may be concerned in its synthesis in so far as they are a factor in the interacting cytoplasmic system, but there are no visible morphological expressions of this functioning. (2) The accumulations of aequeous substances in the cytoplasm in the form of droplets stainable vitally by neutral red, ‘vacuoles,’ are the forerunners of the first yolk. During the building up of the yolk the aequeous droplets become more and more dehydrated and lose their capacity for being vitally stained. (3) These aequeous vacuoles give the impregnation results commonly ascribed to the Golgi apparatus and are interpreted as such. Special emphasis is laid on the question of the identification of the Golgi apparatus. (4) The fat arises de novo in the cell independently of the mitochondria or the vacuoles. It becomes dispersed throughout the cell among the yolk plates, and the lipoidal content of the latter increases at the end of vitellogenesis, when the fatty globules are intimately pressed in among the yolk plates. (5) At a late stage in the growth of the yolk plates there is the sudden appearance of large quantities of glycogen in the perinuclear zone and throughout the cytoplasm.
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    Journal of Morphology 45 (1928), S. 259-292 
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    Notes: The digital disks of the tree frogs are covered ventrally with a superficial layer of vertically elongated, fibrous, and distally free cells between which there empty a series of convoluted mucous glands. The latter are surrounded and, in the larger-disked species, divided into blocks by sheets of collagenous fibers. The glands are emptied by the squeezing together of the collagenous fibers when the body weight exerts a pull on the terminal phalanges. The disks function by friction, cohesion, and adhesion.The digital-disk apparatus was fully established before certain groups of frogs became arboreal. It is retained in others which have reverted to the terrestrial habit. The intercalary cartilage increases the efficiency of the apparatus. It did not arise in phylogeny until after the apparatus was developed.As the digital disks vary in extent in both arboreal and terrestrial species, arborealism seems to have resulted from a chance occurrence of large disks in the smaller-bodied forms; at least, there is no progressive modification of the digits toward particular habitat requirements.The subarticular tubercles of many Salientia develop typical climbing apparatus. This may or may not be correlated with an arboreal habit. In the species with the largest subarticular tubercles no apparatus is present. Arboreal salamanders exhibit no special climbing mechanism, but adhere by pressing their moist integument against the substratum.
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    Journal of Morphology 45 (1928), S. 293-398 
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    Notes: Blindfolded persons walk, run, swim, row, and drive automobiles in clock-spring spiral paths of greater or less regularity when attempting a straightaway. The spirals turn either right or left in one and the same individual, and may do so even in one experiment. But either right or left turns predominate in the great majority of individuals, often to a high degree. The paths show marked individuality, and there is some ground for thinking there exists a correlation between temperamental differences and general character of path.The mechanism which produces the spiral path is not located in the locomotor organs, but in the central nervous system and is probably identical essentially with the spiral mechanism in other motile organisms, all of which move in spiral paths when there are no guiding senses to direct the path. The clock-spring spiral in man is interpreted as the expression in two dimensions of space of a helical spiral mechanism which seems to exist in all motile organisms moving in three dimensions of space and in amebas which move in two dimensions. In a large number of lower organisms the number of body lengths per spiral turn is almost constant, being about 4.5. The smallest regular swimming spirals in man are very close to this value, but the smallest regular walking spirals are somewhat larger. The fundamental spiral mechanism seems to be of molecular dimensions, and there seems to exist a demonstrable locomotor bilateral asymmetry in very nearly, if not quite, all organisms.
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    Journal of Morphology 45 (1928), S. 399-439 
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    Notes: In this study the problem of the tonsil is considered in anurans. The common toad (family Bufonidae) is used as the type, and representative species of the other families are compared.In each species representative stages beginning before transformation were selected, and the lingual region of each was sectioned. Some thyroid-fed toad tadpoles which had prematurely transformed were examined. The investigations led to the following conclusions: 1Accumulations of lymphocytes occur in all the families except Hylidae.2A pair of tonsils located on either side of the tongue appear before transformation in Bufo, and persist, increasing in size through old age.3This pair has its developmental origin at or near the cephalic end of pouch II. In no other species examined do the tonsils appear as early; in almost all forms the accumulations are inconstant in occurrence, as are also some in Bufo.4The cells of the ‘tonsils’ are lymphocytes of varying sizes. They arise from the mesenchyme; later their accumulations become sites of lymphopoiesis.5This type of lympho-epithelial mass is simple in structure and has a greatly thickened epithelium, due to extensive infiltration by lymphocytes. In the connective tissue the vascular supply is abundant.6The differentiation of lymphocytes may be due to a factor of strain, arising through adjustments made during metamorphosis.7Thyroid-fed toad tadpoles transform, apparently without developing tonsils.
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    Journal of Morphology 45 (1928), S. 441-471 
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    Notes: The septomaxillary bone is described in the various families of the urodeles in which it occurs. Its identity as a hitherto unrecognized cartilage bone of the skull is established and its close relationship with the nasal muscles followed through the group. Its presence or absence, which is found to be another criterion for the recent classification of the urodeles as proposed by Dunn and Higgins, is correlated with the development of the accessory dilatator muscle, since it occurs only in groups where this muscle attains an appreciable size.
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    Journal of Morphology 45 (1928), S. 505-535 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The relation of the hepatopancreas to the pyloric stomach and its physiologic histology were studied. The organ consists of two lobes, united ventrally, which lie along the cardiac and pyloric stomachs and the intestine. Primary and secondary lobulations (acini) are present, and the entire organ is a system of anastomosing tubules (lumina). The tubules progressively converge and form a duct in each lobe which leads ventrolaterally into the pyloric stomach.Each acinus consists of a single layer of hepatic and pancreatic cells supported by a basement membrane, and the interacinar spaces are the seat of fibro-elastic tissue and phagocytic cells. The supporting tissue is laminar with that of the stomach. The arterial capillaries, composed of endothelial cells, lie in the interacinar spaces. The blood supply is by way of the basement membrane to the cells.The hepatic cells of specimens collected in September bear little fat; cells of June specimens are laden with fat. Glycogen is deposited in the hepatic cells; there is no difference between the quantity found in September and in June. The hepatic cells probably contain biliverdin. Chemical analysis indicates the presence of trypsin, amylase, and lipase.A review of the literature and a discussion of homologies with reference to the vertebrate liver are given.
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    Journal of Morphology 45 (1928), S. 473-503 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A detailed study has been made of the anatomy of one of the fingernail shells, and preliminary observations on the life-history have been carried out. In its general organization Sphaerium notatum is very similar to the larger fresh-water lamellibranchs. A gastric shield, crystalline style, and style sac, very similar to those found in the stomach and intestine of Lampsilis, are present. A pair of slender muscles extending from the dorsal side of the body into the gills, and evidently not previously described, have been found. The nervous system consists of the typical three pairs of lamellibranchiate ganglia, with their connectives, accessory ganglia, and nerve fibers. Particular study was given to the statocysts and osphradia, and attention is called to the fact that the function commonly ascribed to the osphradia is incompatible with their position in the roof of the cloacal chamber.S. notatum, like all the Sphaeriidae, is hermaphroditic and viviparous. The gonads are paired racemose glands lying behind and below the stomach. The sperm-producing follicles form the anterior portion of each gonad and are somewhat smaller and more numerous than the ova-producing follicles which form the posterior portion. The young pass through the early stages of development in brood pouches in the gills and are expelled as relatively enormous individuals.Preliminary observations on the life-history indicate that reproduction reaches its height in the summer and that fertilization probably takes place during the late summer and fall.
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    Journal of Morphology 46 (1928), S. 217-239 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Notwithstanding the fact that several species of Bruchidae have been used by geneticists for several years, no cytological studies have as yet been made on any member of this family of the Coleoptera. The present paper gives a general account of the spermatogenesis of Bruchus quadrimaculatus Fabr.The spermatogonia undergo two mitotic divisions. After the second division, the nuclei remain small and very dense for some time before the beginning of the growth phase. During this interval the nuclei do not assume again the characteristics of the interkinesis stages. In the primary spermatocytes typical tetrads are formed. The chromosomes are asymmetrically V-shaped. The end of one arm of the ‘V’ fuses with the end of the corresponding arm of its synaptic mate. Disjunction takes place in the primary spermatocyte division. After the division of the secondary spermatocytes, the chromosomes become vesicular and form a reticular nucleus in the spermatid, after which the chromatin becomes deposited as a chromatin rim around the nuclear periphery. The diploid number of chromosomes is nineteen in spermatogonia and in male somatic cells, and twenty in female somatic cells. An unpaired X chromosome is present in the spermatogonia, which fails to divide in the primary spermatocyte division, but passes as a whole to one pole in advance of the autosomes. The X chromosome divides normally in the secondary spermatocyte division with the autosomes.In the method of sex determination, Bruchus does not follow the method of the majority of beetles, since most of those studied adhere to the X-Y type.
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  • 76
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    Notes: The following species of earwigs are used in this study: Labidura bidens, Labia minor, Anisolabis annulipes, Anisolabis maritima, and Forficula auricularia.1In all species the chromosomes are divisible into, a) autosomes and, b) XY-complex.2The chromosome distribution in regular in Labidura bidens and Labia minor. The male diploid number is 12 and 14, respectively. Each has an XY-complex in which the X is a single chromosome.3In both Anisolabis annulipes and Anisolabis maritima the male diploid number is 25, or 22 autosomes and an XXY-complex. The two X components remain fused during the first spermatocyte division.4The diploid number in the male of Forficula auricularia is 25 and 24. The chromosome number is constant in the individual. The irregularity is interpreted as due to the fusion of the two X components in the individuals with 24 counts and to these X components remaining separate in the earwigs with the 25 counts.5An explanation is given for some of the variable results obtained in former studies of the chromosomes of Forficula auricularia.6The discussion considers the possible origin of the variations in chromosome numbers in the earwigs.
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    Journal of Morphology 46 (1928) 
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    The breeding season of the opossum (Didelphis virginiana) and the rate of intrauterine and postnatal developmentThe work on the opossum was begun at the suggestion of Dr. J. T. Patterson, Professor of Zoölogy, the University of Texas, about 1913. It was prosecuted intensively through the generous financial aid and moral support of The Wistar Institute, Dr. M. J. Greenman, Director, and with the assistance of Dr. C. H. Heuser, then fellow of The Wistar Institute. It is to the skill of Doctor Heuser that most of the photographs presented in the four plates accompanying this article and former papers of this series are due. Some of the photographs were taken from fresh living material in January and February of 1917 at Austin, Texas. The embryological investigations soon gave way in large measure to physiological studies in which the following generously aided: Mr. H. A. Wrocbanker, and Mr. Herman Becker, merchant, Austin, Texas; the University of Texas, Department of Zoölogy; The Bache Fund of the National Academy of Science. I take this opportunity of reiterating my indebtedness to these sources of the necessary nervus rerun to carry on the work and for the spirit of helpfulness in which the grants were made. The Wistar Institute is the repository of most of the material collected and will supervise its study in the future. The present writer can primsie only two more installmetns of these ‘studies’: one on the origin of the mesoderm and the chorda dorsalis, the other on pathological ova of the primitive-streak stage and earlier. (1928)
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    Journal of Morphology 46 (1928), S. 143-215 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The breeding season of the opossum at Austin, Texas, begins in January, following a three months' anoestrous period. The modal point for ovulation days is reached in the third week. The rate of intra-uterine development was investigated chiefly by surgical removal of one uterus, noting the stage attained by the ova therein and allowing the surviving uterus to incubate its ova a precalculated period of time. Unique charts epitomize the results. The primitive-streak stage is completed, the medullary groove and chorda begin at seven and one-half days post coitum, seven days post ovulationem, leaving only five and one-half days' actual development of the embryo to birth. The rate of development is compared with Eutherian mammals.The curve of postnatal growth has the shape of embryonic growth curve of higher mammals. The eyes and lips open, at about fifty days (young the size of mice). At this time the young leave the teat for the first time, but are not weaned for about thirty days more. Soon after weaning, the mother may become pregnant again. At ninety to one hundred days (young size of large rats), the young may begin to shift for themselves.
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    Journal of Morphology 46 (1928), S. 317-397 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: In this study observations are reported upon the morphological differences between the three-toed and two-toed forms of sloths, as well as a comparison made of some aspects between the sloths and the other groups of the Xenarthra. Much attention has been paid to the gross, as well as the histological examination of the viscera, musculature, and the vascular and lymphatic systems.The importance of the correlation of the morphological findings with physiological studies has been emphasized. For example, the probable correlation of the vascular plexuses of the extremities with the postures and muscular activity of the different members of the Xenarthra is discussed. Much new information has been gained concerning the placentation and development of the sloths, as well as concerning the structure of the male and female reproductive tracts.
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    Journal of Morphology 46 (1928), S. 399-430 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The septomaxillary is described in certain anurans and in some of the reptiles in which it occurs. In urodeles and some anurans this bone arises by ossification of the nasal cartilages. Lack of embryological material has prevented the verification of this in the young stages of the reptiles. Adult reptiles have been examined, and in these the bone appears to be and has often been described as a ‘membrane bone.’ It is suggested, however, that the septomaxillary is originally a ‘cartilage bone,’ and that in the reptiles additional membrane bone layers form its main part and obscure its cartilaginous origin. The infolding of the bone in the anurans and reptiles until it lies in close contact with the nasal septum, and thereby loses contact with the external nasal structures, appears to be correlated with the loss of the external nasal muscles. This loss in its turn results from the adoption of terrestrial life and consequent changes in the respiratory mechanism.
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    Notes: This study deals with the seasonal distribution of protozoa (February, 1927, to February, 1928) in correlation with seasonal fluctuations of temperature, hydrogen-ion concentration, and the relative amounts of dissolved oxygen and other gases in a small fresh-water pond. Twenty-seven species of Sarcodina, thirty-one species of Mastigophora, and 109 species of Infusoria were recorded in the surface water of the pond.As found especially for Mastigophora and Infusoria, the number of species is inversely correlated with the abundance of individuals in the seasonal distribution.Higher temperatures probably accelerated the rate of reproduction, since the seasonal maxima for most of the species were recorded in warmer weather.Colonial flagellates and Zoochlorellae-bearing ciliates seemed to be favored by higher oxygen content, with a simultaneous abundance of volatile acids, especially CO2. Although hydrogen-ion concentration was limited between 6.2 and 7.05, it was probably one of the factors influencing protozoan distribution, since several species disappeared when the lowest pH was recorded. Sunlight is one of the important factors in bringing certain heliotropic protozoa to the surface.The seasonal maxima of many of the protozoa occurred during September and October, 1927, when most of the observed physical environments seemed much more favorable than in other months.
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    Journal of Morphology 46 (1928), S. 479-519 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Series of injections of ovarian hormone have been made into normal and ovariectomized immature animals. Injections were made twice daily for twenty-two days. The total dose exceeded 1000 rat units per animal.Effects noted in the living animals were the appearance of reddening and swelling of the ‘sexual skin’ and change of the cell content of the vaginal smear to the interval type of the mature animal. Measurements made at operation, before and after injections, indicated considerable enlargement of both the cervix and body of the uterus. The thymus glands of the injected animals weighed significantly less than those of the controls. Histologic study of the genital tract showed extreme thickening of the vaginal walls, considerable growth of the uterine epithelium and glands, hypertrophy of the muscle layers of the uterus, and advanced differentiation of the epithelium of the uterine tubes.The ovaries of the injected normal animal were smaller and contained fewer primordial and medium-sized follicles than those of the controls. The presence of large numbers of atretic follicles, especially large flattened scars from former relatively well-developed follicles also suggests a harmful effect of this amount of ovarian hormone upon follicular development. Several stages of elimination of ova from polyovular follicles were also observed. There was marked growth in the ducts and an increase in the number of alveoli of the mammary glands.
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    Journal of Morphology 46 (1928), S. 563-583 
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    Topics: Biology , Medicine
    Notes: The urinogenital organs of Myrmecobius fasciatus conform to the marsupial type in both their anatomical characters and histological details. The external genitalia indicate a close relationship with the Dasyuridae.
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    Notes: This peritrichous ciliate lives as an ectocommensal on the skin and gills of anuran tadpoles. Its relation to described species of Trichodina is doubtful. This study was made almost exclusively on fixed and stained material. Binary fission is similar to that in other ciliates. The horseshoe-shaped macronucleus condenses, then divides amitotically. The single small micronucleus forms a spindle containing between four and six chromosomes.Endomixis is of high incidence in the free-living Trichodinae. Encystment was not observed. At the onset of endomixis, the macronucleus disintegrates into fragments which persist throughout the process. The micronucleus undergoes three rapidly succeeding mitotic divisions to form eight nuclei. There is no evidence of chromosome reduction during these divisions. Seven of the nuclei differentiate into macronuclear anlagen; the eighth becomes the functional micronucleus. Successive cell divisions - before each of which the micronucleus divides - distribute macronuclei to daughter cells. Variations from the regular process of endomixis may arise, 1) by precocious division of endomictic parents; 2) by extra divisions of the micronucleus; 3) by less than the usual number (three) of divisions of the micronucleus; 4) by hypertrophy and early differentiation of the micronucleus into macronuclei; 5) by unusual segregation of nuclei to daughters, and, 6) from miscellaneous causes.The significance of these variations is discussed in connection with the possible origin of bimicronucleate and amicronucleate races.
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    Journal of Morphology 47 (1929), S. 1-36 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The first spermatocytes of Circotettix verruculatus have eleven chromosomes. Five of these are regularly atelomitic and three are telomitic. The other three are variable and may have both diads telomitic, both atelomitic, or one diad telomitic while the other is atelomitic. The locus of fiber attachment and, consequently, the form of the chromosome are constant for the individual. The point of fiber insertion is known to be inherited according to mendelian principles, and is, therefore, a measure of the frequencies of the telomitic and atelomitic diads in a group of individuals.Samples of five geographically different populations were studied with respect to the proportion of atelomitic to telomitic diads in the three variable tetrads. The proportion for each of the three chromosomes was compared with that for the corresponding tetrads from the other localities. The data were subjected to statistical analysis, and significant differences between some of the groups were found in the proportion of atelomitic to telomitic diads in corresponding chromosomes.A possible correlation between these cytological differences among the various localities and the formation of geographical races or subspecies are discussed. An inversion of the portion of a chromosome, which causes an apparent, although not a real, change in the locus of fiber attachment, is suggested as the origin of atelomitic chromosomes. The effect which heteromorphism of synaptic mates may have on crossing-over is considered.
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    Journal of Morphology 47 (1929), S. 37-87 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The vesicular nucleus of this amoeboflagellate is similar in structure in both phases of its life-cycle. It has a fairly large caryosome surrounded by a pericaryosomal area in which there are small oxyphilic pericaryosomal granules on a fine reticulum. On the inner surface of the definite caryotheca is a layer of epithecal chromatic granules.Nuclear division is similar in both amoeba and flagellate phases. During the prophase the nucleus enlarges, and the expanded caryosome becomes resolved into basophilic and oxyphilic components and assumes either an oblong, dumb-bell, or spindle shape. The pericaryosomal granules enlarge, shift about, and eventually become arranged in an equatorial band around the elongated caryosome. In the metaphase the equatorial plate of chromosomes appears after the inward migration of the pericaryosomal granules, accompanied by the formation of a definite intranuclear spindle, usually with polar masses, polar granules, and a centrodesmose. After the poleward migration of the daughter plates of chromosomes in the anaphase, the telophase constriction of the nuclear membrane produces two daughter nuclei with a portion of the spindle remaining outside. The epithecal layer of granules remains in place on the nuclear membrane during the entire process of mitosis. Plasmotomy normally follows mitosis, but may be delayed, giving rise to multinucleate individuals. In the flagellate the blepharoplast usually divides simultaneously with, but independently of, the nucleus. There are many divergences in the details of mitosis, but these are thought to be variations of one type of division rather than examples of different processes.
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    Journal of Morphology 47 (1929), S. 89-133 
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    Notes: During the telophases each chromosome becomes inclosed in an individual sac or vesicle which, together with its contents, is called a chromosomal vesicle. The vesicular membrane is of cytoplasmic origin, but is formed under the influence of the chromosome and a droplet of karyolymph. A precise numerical correspondence between chromosomes and chromosomal vesicles has not been established, but it is evidence that most, if not all, of the chromosomal vesicles retain their individuality during the resting stage and until after the new chromosomes have been fully formed.The transformation of the telophase chromosome into the reticulum of the resting stage and the manner in which a new chromosome is formed from a portion of this reticulum are described in detail. In the early prophases each developing chromosome is embedded in a sheath or matrix of less deeply basophilic material, which disappears before the middle prophase is reached.The formation of chromosomal vesicles is interpreted as a device for doing more rapidly and effectively, under stress of special circumstances, the work that the nucleus must accomplish during the so-called resting stage.
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    Journal of Morphology 47 (1929), S. 135-199 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Definite information concerning the time of development and location of the different imaginal discs of Drosophila melanogaster was needed in order to interpret especially the gynandromorphs, mosaics, and intersexes that have been extensively reported in cultures of this fly. This information was also desirable for many of the mutant types. It was not known, for example, when an organ was reduced or absent, whether its imaginal disc showed a corresponding reduction, or whether it was full size in the larvae and pupae, and failed to carry through to the later stages.Three mutant types with eyes smaller than those of the wild type, namely, lozenge, bar, and eyeless, were examined. It was found that there is a corresponding difference in size as far back as the imaginal disc could be detected. Similarly for the two mutants, vestigial and no-wing. Conversely for the mutant, bithorax, in which the metathorax is larger than the normal and has assumed many of the characters of the normal mesothorax, the imaginal disc was correspondingly enlarged.It follows that the effects of the mutant genes for these characters can be observed in the very earliest condition of the imaginal disc.
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    Journal of Morphology 47 (1929), S. 201-225 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: There are eleven pairs of chromosomes in the somatic cells of the opossum.The sex chromosomes are of the x-x type in the female and the x-y type in the male.The number and type of the chromosomes are constant in the wide variety of tissues and organs studied, except that one dividing giant cell of the spleen showed an 8n number of chromosomes.The arrangement of the chromosomes in equatorial plates is that of an autosomal ring surrounding the centrally located sex chromosomes.
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    Journal of Morphology 47 (1929) 
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    Journal of Morphology 47 (1929), S. 435-478 
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    Notes: The perivisceral fluid of Pheretima indica (Horst) contains five types of leucocytes: lymphocytes, monocytes, granulocytes, lamprocytes, and linocytes. The granulocytes differentiate either from free lymphocytes, from peritoneal epithelial cells lining the leucocytopoietic organs, or from lymphocytes (hemocytoblasts) embedded in these organs. The lymphocyte is a hemocytoblast. The eosinophilic granulocyte is the most numerous of the several types of granulocytes. Morphologically and tinctorially, it resembles the eosinophil of fishes. The eosinophil granule is thought to arise either by a ripening of a basophil granule and to pass through a metachromatic phase during this process, or by being formed immediately without such a ripening process in small hemocytoblasts. The stimulus for the excessive production of eosinophils is thought to be the degree of infection of the leucocytopoietic organs by a species of the gregarine, Monocystis.A series of segmentally arranged leucocytopoietic organs is described for the first time in the oligochaetes. These organs are essentially foldings of the septa and offer sacculations in which leucocytopoiesis may take place.A discussion of the possible phylogeny of the hemocytopoietic organs of the invertebrates and vertebrates is given.
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    Journal of Morphology 40 (1925), S. 235-259 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A study of the peripheral nerves of the earthworm shows that one pair of nerve trunks arise from the lateral regions of the cerebral ganglion, one pair from near the lateral, and two pairs from the ventral region of the circumpharyngeal connectives. These supply, in the order given, the prostomium, segment 1 and segment 2. Segment 3 and each succeeding segment, except the last, are supplied with three pairs of nerve trunks which arise from the nerve cord in the segment concerned. None of the nerve trunks of the body was observed to send branches to more than one segment, which shows that they are segmental in origin and distribution.The anterior portion of the central nervous system has undergone caudal migration and modification of its ganglia. Some of the nerve trunks have disappeared through atrophy, while others have become fused at their bases.A subepidermal nerve plexus is found at the base of the epidermal cells from which nerve fibers pass to the internal nerve net and to the central nervous system. This plexus also sends intercellular and intracellular fibers into the epidermis.The so-called sense cells of the epidermis appear to be the cell bodies of sensory neurones which send nerve fibers to the ganglia of the central nervous system, where they form synaptic connections with other neurones.There is an enteric nerve plexus in the wall of the alimentary canal which is directly connected to the circumpharyngeal connectives.
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    Journal of Morphology 40 (1925), S. 341-416 
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    Notes: Astylosternus robustus has greatly reduced lungs. All Amphibia exhibiting such a reduction have their epidermis either penetrated by capillaries or thinned to facilitate greater cutaneous respiration. The epidermis of both sexes of A. robustus is penetrated by capillaries. The «hairs» of the adult male are merely extensions of this vasculated epidermis to compensate for the greater muscularity, size, and activity of this sex.The digits of terrestrial urodeles do not serve as special centers of cutaneous respiration. Digital sinuses are present in all urodeles. The abdominal and femoral tubercles of arboreal and some terrestrial frogs may function greatly in respiration, for their epidermis is penetrated by capillaries.All urodeles and frogs having well-developed and frequently emptied lungs possess a functionally complete auricular septum and a spiral valve. Injection experiments demonstrate a complete separation of arterial and venous blood in living specimens. A reduction of the lungs conditions a reduction of the left auricle, but disuse causes no change in size. A great decrease of the lungs, or even a disuse of them, conditions a fenestration of the auricular septum and a loss of the spiral valve. The spiral valve is formed by a backward growth of one of the synangial valves and is not homologous with the accessory valves of dipnoans. Lungless salamanders have no left auricle and no spiral valve.
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    Journal of Morphology 40 (1925) 
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    Journal of Morphology 48 (1929), S. 45-79 
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: It was found that thyroid deficiency in the albino rat (Mus norvegicus albinus) is followed by a trend to increased concentration of epinephrin in the suprarenals. The basis of this lies in the relatively greater retrogression of the cortex as contrasted with the medulla which becomes a relatively greater proportion of the organ as a whole. Confirmatory evidence is found in cell counts per unit area and the part of the disappearance of lipoid from the cortical cells of the suprarenals of thyroidless animals.
    Additional Material: 5 Tab.
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  • 96
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 48 (1929), S. 81-103 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A comparative study of the embryology of the rabbit in races of large and small adult size shows a consistently more rapid rate of cell multiplication and of increase in mass in large-race embryos than in those of small race.This more rapid rate of growth is transm tted by and influenced equally by sperm and egg cell, as is shown by the results of reciprocal crosses.Rate of differentiation is independent of rate of growth and unaffected by it. Consequently, embryos of the large race have attained greater size than those of the small race at corresponding stage of differentiation.The fundamental difference in rate of growth is already in evidence in forty-eight-hour embryos and becomes increasingly clear at later stages. Embryos produced by the large race have undergone about one more cell division at forty-eight hours after mating and so are approximately in the thirty-two-cell stage when embryos of the small race are in the sixteen-cell stage.
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  • 97
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 48 (1929), S. 105-121 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Two types of cytoplasmic inclusions, differing in reactions to vital dyes and to osmic fixation and impregnation have been demonstrated in Peranema trichophorum. The mitochondria are rod-like and lie in more or less spiral rows, forming a single layer beneath the periplast. They are stained supravitally with Janus green, but not with neutral red. They may be demonstrated by staining in iron hematoxylin after Mann-Kopsch fixation. They are also blackened in prolonged osmic impregnation, but are bleached readily with hydrogen peroxide.The small spherical osmiophilic inclusions are scattered in distribution, although sometimes more numerous in the anterior third of the organism. These bodies are stainable supravitally with neutral red, neutral violet, and brilliant cresyl blue. They are densely blackened in osmic impregnation, and are not bleached in the usual treatment with hydrogen peroxide. They are not however, demonstrated by Mann-Kopsch fixation and iron hematoxylin. After being stained supravitally with neutral red, these inclusions may be blackened under direct observation by exposure to osmic vapor in hanging-drop preparations.
    Additional Material: 1 Ill.
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  • 98
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 48 (1929), S. 123-151 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: From a study of over 1000 mothers, the female chromosome number appears to be 2N = 22; N = 11. The male number has not been exactly determined, but is presumably not haploid. Only one maturation division occurs in the parthenogenetic egg, and the authors have seen only one in the sexual egg. During the growth stages of the eggs, the chromatin is totally obscured by a large amount of deeply staining nucleolar material which exhibits several phases. Ultimately, this material is apparently absorbed into the ooplasm. Just before the egg is laid, the ovoid chromosomes, in late prophase or in metaphase, are seen in a germinal vesicle situated always at one side of the egg. The maturation division occurs immediately after egg laying. A degenerate body, hitherto undescribed, is noted in the ripe parthenogenetic egg, situated at the pole opposite the germinal vesicle. It is believed to arise by reorganization of nucleolar substance. The body in the sexual egg desribed by Weismann and Ishikawa ('91) as the Paracopulationzelle is noted and its interpretation by these authors questioned, but, for lack of sufficient evidence, no counter-explanation is offered. The possible relation between experimental sex control and the time of maturation division in the parathenogenetic egg is discussed.
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  • 99
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 48 (1929), S. 153-171 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A description of the gross embryology of the sex apparatus of a common diplopod, the corn millipede. The life-cycle of this animal involves eleven instars extending over a period of three years.In the male the true first legs are shed at the ninth ecdysis and the large clasping appendages are substituted through the last three instars. In the region of the second body somite the fused coxal plate and the penes are developed at the final molt; the second appendages are reduced at this time. The greatest changes occur in the region of the seventh somite, where the legs are shed about the eighth ecdysis and the gonopods developed through the remaining instars. It is evident that these gonopods arise as a modification of the sternites of the seventh somite.In the female the second legs are reduced to vestiges at the final molt. The structures at the mouth of the oviducts are developed from the surrounding tissues and the modified sternites of the reduced second legs. These changes are in progress as early as the seventh instar, but the greatest changes occur at the final ecdysis.
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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 48 (1929), S. 173-251 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The purpose of this study was to determine whether structural elements of the cytoplasm can be demonstrated to be specifically concerned with certain physiological processes that are experimentally induced in tissue at the time of fixation. The methods for bringing into view variations in cell structure correlated with cell activity were as follows: the increase of the process of secretion by subcutaneous injection into the living animal of phenol red and of urea; the increase of the process of reabsorption by injection of glucose: the inhibition of reabsorption of sugar by injection of phlorhizin.Variations of the same magnitude in the form, position, quantity, and interrelationships of granules, globules, chondriosomes, and Golgi substance were found to occur in normal untreated animals and in those treated experimentally. Some evidence was found that in cells of the proximal tubule a characteristic form of Golgi body appears which seems to be correlated with increased reabsorption of sugar.
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