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  • Life and Medical Sciences  (60)
  • 1980-1984
  • 1925-1929  (60)
  • 1927  (31)
  • 1925  (29)
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  • 1980-1984
  • 1925-1929  (60)
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  • 1
    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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  • 2
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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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  • 3
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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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  • 4
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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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  • 5
    Electronic Resource
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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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  • 6
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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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  • 7
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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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  • 8
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    New York, NY : Wiley-Blackwell
    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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  • 9
    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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  • 10
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    New York, NY : Wiley-Blackwell
    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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  • 11
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    New York, NY : Wiley-Blackwell
    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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  • 12
    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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  • 13
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    New York, NY : Wiley-Blackwell
    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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  • 14
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    New York, NY : Wiley-Blackwell
    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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  • 15
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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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  • 16
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    New York, NY : Wiley-Blackwell
    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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  • 17
    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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  • 18
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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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  • 19
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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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  • 20
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    Journal of Morphology 44 (1927), S. 363-372 
    ISSN: 0362-2525
    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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  • 21
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    Journal of Morphology 41 (1925), S. 239-265 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    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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  • 22
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    Journal of Morphology 44 (1927), S. 127-216 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    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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  • 23
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    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 40 (1925), S. 235-259 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    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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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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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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  • 28
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    Journal of Morphology 41 (1925), S. ii 
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  • 29
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    Notes: A special type of cell, called ‘Lichtzellen’ by Hesse, was found in the photosensitive regions of the earthworm. Wherever the epidermis is most sensitive to light these cells are most abundant. They are found in the epidermis of all segments of the body and also in nerve enlargements of the prostomium and the caudal segment, but the intersegmental and ventral regions of the different segments, except the more distal ones, contain none of them. They are supplied by nerves and each contains a characteristic inner structure, the optic organelle, composed of a large central hyaline structure, the lens, which is surrounded by a dense network of nerve fibrillae, the retinella. In hanging drops the lens was found to focus light in the region of the retinella irrespective of the direction of the rays.These cells are similar in structure and function to the visual cells in leeches. Available data indicate that these cells function as photoreceptors and that the fibrillae of the retinella are the direct receptors of light stimuli.Pigment is not associated with the photoreceptors in a way that suggests direct functional relationship, but there is a subepidermal pigment layer through which pinhole windows admit light along the path of nerves to each of the nerve enlargements containing photoreceptor cells. These windows open in such directions as to determine the direction of withdrawal of the worm.
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    Journal of Morphology 41 (1925), S. 95-157 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This paper represents the third part of a monograph on the development of the lymphatics and lymph hearts of Anura. In this part are considered the origin and development of the subvertebral, lateral, and dorsal lymphatics of the trunk, the caudal lymphatics, and the posterior lymph hearts.The chief lymphatic trunks arise along the veins from a series of small, spindle-shaped, and discontinuous anlagen which subsequently coalesce and thus establish continuity with one another. Lymph plexuses are formed from which emerge the main secondary lymph channels. After such trunks are laid down as indicated, smaller branches and capillaries spring from them by sprouting or extension, due to their actively proliferating endothelium.The posterior lymph hearts ‘crystallize,’ so to speak, from localized areas of the lateral lymphatic plexus. During its reorganization and differentiation, it temporarily separates from the surrounding lymph plexus. Other genetic details, such as the formation of its valves, histogenesis of its walls, number of hearts laid down, etc., are also considered. Twenty-two figures (microphotographs and reconstructions) accompany the text.
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    Notes: In general, the changes of locomotor rate of Amoeba under the influence of temperature are similar to the effects of temperature in other biological processes.The rate increases with rising and decreases with falling temperatures within a certain temperature range, this being, for the forms investigated, the interval between 6° and 23.5°C. In some individuals, however, these limits were found to be wider, extending from 2° to 26°. There is an average optimum at about 23.5°, beyond which an increase in temperature is followed by a decrease in rate. The immediate response of Amoeba to a change of temperature is variable, due, as was shown in a previous paper, to the fact that locomotor-rate changes are rhythmic. The effect of a change of temperature is thus conditioned not only by the enviornmental factors, but also by the phases of the locomotor rhythm. This fact also makes it difficult to establish the exact quantitative relationship which exists between a change of temperature and the locomotor rate - an aspect which will be developed in a future paper.
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    Notes: A system of fibers has been found in Dileptus gigas which is probably a neuromotor apparatus. A distinct elongated basal rod, found near the base of the gullet, gives rise to three sets of fibers: (1) a set of heavy fibers radiates out around the funnel-shaped gullet; (2) a pair of heavy fibers pass directly from the basal rod to the band of trichocysts, one on each side, extending to the tip of the proboscis; (3) a set of very delicate branching fibers is distributed over the surface of the organism.This system of fibers is held to be a neuromotor apparatus, because, (1) the general structure and appearance of the fibers suggest a neuromotor function and, (2) there is little or no evidence indicating any other function; and because, (3) the fibers in this system are connected to the most highly specialized structures in Dileptus, and, finally, because, (4) they are similar to structures found in other forms for which a neuromotor function has been experimentally demonstrated.
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  • 34
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    Journal of Morphology 44 (1927), S. 417-465 
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    Notes: Observations indicate that this Balantidium from the guinea-pig is Balantidium coli, the form found in the pig and man. The lengths and breadths of this Balantidium and the ratios of length to breadth are very close to the measurements and ratios given by McDonald for B. coli. When plotted, the body lengths of the guinea-pig parasites appear in two groups, the smaller individuals being the exconjugants. Many of these exconjugants resemble Neiva's B. caviae. The structure of the Balantidium from the guinea-pig is essentially identical with that of B. coli as given by McDonald.Fission and conjugation of this ciliate follow the general course found in a number of other ciliates. During fission the micronucleus divides and the daughter micronuclei migrate to each end of the macronucleus before the latter divides. In conjugation there are two divisions of the micronucleus, one of these nuclei dividing to form the pronuclei. Pronuclear exchange and fusion are followed by a heteropolar division of the synkaryon, resulting in the formation of the new macronuclear and micronuclear anlagen.The parasite was found in the intestinal tissue of the host. No reproductive stages were found in the cysts. New hosts are invaded through contamination of the food and drink with the cysts.
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    Journal of Morphology 44 (1927), S. 467-514 
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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 eggs of Corella develop in the atrial chamber of the parent at a pH below that of normal sea-water (pH 7.4 ±). When removed to normal sea-water in early stages and under certain other experimental conditions, larval development is more or less inhibited, the tail being most inhibited, the dorsal region somewhat less. The free larval stage may be eliminated and later development and metamorphosis may proceed normally to an advanced stage in the chorion and give rise to normal ascidians. The region most inhibited are, in general, those which possess the highest reducing power, as indicated by KMnO4. Experiments made in the attempt to control development all agree in indicating that the early stages are adjusted to a certain CO2 concentration approximately that of the atrial chamber and presumably near that of the body. Solutions of the same pH may or may not inhibit development according to their CO2 content.The tail, the region of highest reducing power in the embryo during its development, is most inhibited; the dorsal region, the next most rapidly reducing region, is next in degree of inhibition. All differences in reducing power disappear when, or soon after, the animals are killed by other agents before treatment with KMnO4.
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    Notes: This paper contains a description of the appearance and behavior of the chromatin and chief cytoplasmic inclusions in the male germ cells of three species of Belostomatidae.There are eight spermatogonial chromosomes in Lethocerus americanus, twenty-four in Belostoma flumineum, twenty-eight in Benacus griseus. An XY-pair of sex chromosomes occurs in each species. These are identifiable at every step in maturation in Lethocerus, but not in the others. A clear case of heteropycnosis occurs in Benacus. Parasynapsis is believed to be the mode of pairing of chromosomes in all three species. The genesis of three large atelomitic ring tetrads is described in Lethocerus.Chondriosomes are traced from spermatogonia to spermatids without a break in continuity. Spermatogonial chondriosomes are always granular. During the growth period filaments are formed, probably by fusion of granules, and these are sorted out in approximately equal numbers to spermatids. Benacus is especially favorable for studies on chondriosomes. Likewise, Golgi bodies have been traced throughout the process of maturation. They are minute granules in spermatogonia. During the growth period each becomes a flattened plate-like body clearly differentiated into two materials. Dictyosomes are formed by fragmentation in the first prophase, and these are distributed to spermatids where they fuse to form an acroblast in each. Some minor cytoplasmic inclusions are briefly described.
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    Notes: By the use of a satisfactory technique, excellently preserved spermatogenetic tissue was had both for Rattus rattus and Rattus norvegicus. The careful examination of twelve spermatogonial cells of the former species and of twenty in the latter species shows that R. rattus has forty diploid chromosomes and R. norvegicus, forty-two. A careful examination of the haploid cells of both species, both in the first and in the second spermatocyte divisions, confirms the diploid determinations.Both species have an unequal pair in the spermatogonial divisions and the finding of a similar unequal pair in the first spermatocyte division constitutes the evidence for an X-Y mechanism in each. A comparison of the morphology of the first spermatocyte tetrads in the two species reveals the presence of a large K-shaped chromosome in R. norvegicus which is not present in R. rattus. Furthermore, a comparison of the X-Y complex in both the spermatogonial and first spermatocyte divisions shows that these are morphologically different in the two species, the Y in particular being markedly dissimilar in size. A short discussion as to the bearing of these findings on the questions of the origins of the two species and their known intersterility is presented. The marked similarity of the tetrads of the black rat to those described for the mouse is noted.
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    Journal of Morphology 40 (1925), S. 191-233 
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    Notes: Hermaphroditic gonads of Rhabdites elegans can be distinguished in early developmental stages, but oogonia cannot be told from spermatogonia. Certain peculiar males show developmental processes approaching those of hermaphrodites. More eggs are produced by a hermaphrodite than there are sperm with which to fertilize them. Such exhausted hermaphrodites may be mated with males and produce fertile eggs, but convincing evidence of cross-fertilization is lacking. Unmated females of Diplogaster aerivora live longer than mated ones, but no difference was found in the males. Sexual instinct seems to be lacking in males of R. dolichura and R. elegans.Hermaphrodites mated with males produce many more male offspring than by self-fertilization, but these do not exhibit sexual instincts. Females produced by cross-fertilization are not pure females, nor have they been found at all in R. elegans or R. dolichura. After fertilization in these two species, both polar bodies are formed and the pronuclei fuse. Sex is determined by the form of sperm.
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    Journal of Morphology 40 (1925), S. 261-297 
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    Notes: The parasynaptic union of chromosomes associated with the formation of a karyosphere is demonstrated in the spermatocytes of Phanaeus.The twelve V-shaped leptotene threads are polarized with their apices embedded in one plasmosome-like body, their distal ends in another (primary and secondary caps, respectively), and undergo a conjugation of the parasynaptic type. The distal ends of the chromosomes are freed from their attachment in the secondary cap. The six pachytene loops retain their polarized configuration.The basichromatin of the pachytene chromosomes appears ultimately to be withdrawn to form the karyosphere comprising six chromatic bodies within an oxychromatic «plasmosome,» the latter probably derived from the primary cap. The two caps are believed to arise from the chromosomes. The primary cap apparently becomes incorporated again in the chromosomes; the secondary cap, together with linin remnants of the pachytene chromosomes, disintegrates in the nucleus as residual chromatin.In the dissolution of the karyosphere six ring-shaped tetrads emerge arranged in a temporarily connected chain, giving under certain conditions, the misleading impression of twelve components arranged end to end. The entire content of the karyosphere appears to be employed in the formation of the chromosomes; no visible plasmosome remains.
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    Journal of Morphology 40 (1925), S. 299-340 
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    Notes: The course of digestion of an essentially protein food (beef liver) was followed by histological and histochemical methods in Planaria dorotocephala. After an average fasting period of two weeks, the planarians were fed and examined at close time intervals, ranging from one minute to eighty-seven days after feeding. Liver particles are engulfed by the phagocytic cells of the intestine into food vacuoles, where a series of digestive changes occur. The liver particles coalesce into a granular spherule which gradually condenses into a homogeneous and chromatophilic spherule. As the spherule transforms from a granular to a homogeneous condition, it exhibits a gradually increasing affinity for stains, an intensified protein reaction, and a gradual diminution in size. These spherules are protein, since they give positive xanthoproteic and Millon reactions.The homogeneous protein spherules gradually disappear, beginning at about twelve hours after feeding and continuing until the fifth day. During this period fat-droplets form, gradually increasing at the expense of the protein spherules. The protein spherules apparently dissolve into the cytoplasm, furnishing intermediate chemical compounds (tests indicate that a carbohydrate stage does not intervene) from which fat is synthesized. It thus appears that the fat is formed from the protein spherules. The fat thus formed is stored in the phagocytic cells, and remains unchanged in quantity for a fasting period lasting six weeks, after which it gradually diminishes. During the engulfment of the food, the fat decreases markedly, apparently furnishing energy for phagocytic activities. A few of the protein spherules may persist as «protein reserve».
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    Journal of Morphology 41 (1925), S. 267-281 
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    Notes: Of the eggs laid by Fasciolaria about 1 per cent develop into veligers, about 2 per cent more undergo a few cleavage divisions, and about 97 per cent do not divide at all. The 99 per cent that fail to develop normally are ‘swallowed’ by the veligers. This study concerns itself chiefly with the ova that do not divide. Notes on normal development and on the ova that undergo atypical cleavage are included.All of the ova are found to be typical when passed from the ovary. To each ovum one to several sperms become attached at the vegetal pole in the region of a mass of undifferentiated protoplasm - the ‘polar mass.’ A fertilization cone forms in each ovum and a fertilization membrane. In typical development a yolk lobe is formed, the sperm enters in the usual way, and fertilization is completed as in many other mollusks. In 97 per cent of the ova the yolk lobe is not formed and the sperm does not enter. In these cases the wall of the egg nucleus remains intact a long time. The nucleus itself and the ‘polar mass’ sink into the egg and meet at the center. Then the nuclear wall disappears and an atypical diaster is formed. However, cleavage is not begun and the chromosomes form vesicles that remain near the center of the ovum until it is ‘swallowed’ and digested by the veliger.
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    Journal of Morphology 44 (1927), S. 117-125 
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    Notes: In the early cleavage stages of Ascaris the homologous chromosomes are of unequal length. Measurements show that these homologues fall into two sharply defined groups suggesting their biparental origin. The shorter are considered to have come from the male.As the age of the embryo increases, these differences between the chromosome mates tend to become less, and it is suggested that at some later period in the history of the animal this difference will entirely disappear in response to the effect of continued existence in a common environment. The length of the chromosomes is very slightly shortened during the early cleavage divisions, while the area of the equatorial cross-section of the cells becomes enormously reduced.
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    Journal of Morphology 40 (1925), S. 1-109 
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    Notes: Much more information than is available at present must be obtained before the phylogeny of the muscular system in the Teleostei can be worked out satisfactorily. As a step toward the solution of this problem, the present study gives a detailed description of twenty cranial muscles in a number of species belonging to three groups of cypriniform fishes: the Cyprinoids, Cobitoids, and Siluroids.Particular attention is given to the morphological relations of the following muscles: adductor mandibulae, geniohyoideus, levator arcus branchialis, adductor arcus palatini, retractor branchialis dorsalis, interarcualis dorsalis and the trapezius.Comparison is made between corresponding muscles in different members of the three groups of fishes, and various homologies are pointed out between muscles in cypriniform and those in other fishes, especially Amia, Scomber, Perca and Esox.
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    Journal of Morphology 40 (1925), S. 111-167 
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    Notes: Microscopic examination of both living and stained forms indicates that the so-called ‘multivacuolate’ and ‘amicronucleate races of Paramecium caudatum’ belong to the species Paramecium multimicronucleata. The published accounts of the morphology and cultural characteristics of the various forms are compared and provide additional evidence. A more complete description is given, including distinctive characters previously omitted.The conjugation process of P. multimicronucleata in general resembles that of P. caudatum, most of the differences being due to the presence of four micronuclei instead of one. These each divide twice with characteristic figures, twelve of the sixteen daughter nuclei then degenerating. One of the remaining four splits to form a single pair of functional pronuclei in each cell. The two migratory pronuclei interchange as in P. caudatum. The synkaryon divides three times, and probably seven of these nuclei degenerate. The remaining one apparently undergoes two divisions. In most cases by six to eight hours after the conjugants separate two micronuclei of the four thus produced form enlarged macronuclear anlagen, the other two remaining as micronuclei. Each anlage divides within the next two or four hours, producing four macronuclear and four micronuclear analagen. Two fissions, each preceded by a division of the micronuclei, restore vegetative conditions.The process described above is compared with conjugation in P. bursaria, P. caudatum, and P. putrinum.
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    Journal of Morphology 40 (1925), S. 169-189 
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    Notes: A review of the literature of the gastric glands of reptiles shows marked differences of opinion concerning the nature and character of the cells composing the gastric glands.The present investigation of the gastric glands of the alligator has been carried out by histochemical and physiological experiments, rather than by the usual morphological methods, but the results can be stated both in terms of structure and function.1The surface epithelial cells and those lining the gland pits in the fundic, cardiac, and pyloric regions of the stomach of the alligator are not strictly comparable functionally to the mucous cells of mammals.2The cells composing the necks and bodies of the glands in the fundus, according to histochemical reactions, are parietal cells.3Certain cells lying beneath the columnar epithelial cells lining the lumen of the stomach and the foveolae react to one method of fixation and staining as do the chief cells of mammalian material.4The results of the experiment with the vital dye, neutral red, show that the cells of the gastric pits, the necks and bodies of the glands in the fundus of the alligator's stomach, react identically as those of the mammalian stomach.5The gastric juice of the alligator is acid to litmus-paper and contains a free mineral acid.
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    Journal of Morphology 40 (1925), S. 417-459 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development and cytology of cartilage and bone in the limbs from the fifty-second hour of incubation to the first day after hatching are described.The chief points of interest arising from this study are: (1) Chondroblasts when liberated during cartilage resorption die and disintegrate. (2) All the long bones possess structures which, though not undergoing independent ossification, are homologous with the mammalian epiphyses. (3) Endochondral ossification occurs only in the epiphyses and ends of the diaphyses. (4) The marrow cavity contains multinucleated giant cells which appear to be formed by the fusion of degenerating cells.
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  • 50
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    Journal of Morphology 40 (1925), S. 461-477 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Total splenectomy in the frog means practically complete extirpation of the erythropoietic apparatus. Out of sixty-four operations it was followed by: 1Stimulation of erythropoiesis in the kidney (mesonephros), 35 to 46 per cent.2Stimulation of erythropoiesis in the fat-bodies, 5 per cent; lymphocytopoiesis, 8 per cent.3Stimulation of erythropoiesis in the bone-marrow, 11 per cent.4Formation of a new spleen, 8 per cent.5No perceptible erythropoletic stimulation, 24 per cent. The latter leads to a condition of anemia followed by death within about sixty days.Partial splenectomy leads to spleen regeneration.The life tenure of the frog erythrocyte is approximately 100 days.Total splenectomy experiments indicate that the chief function of the spleen in the frog inheres largely in its lymphocyte content and in the transformation of lymphocytes into erythrocytes.
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    Journal of Morphology 40 (1925), S. 517-557 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: An early segregation of germ cells and migration through a germ track into the gonad does not occur in the albino rat. The germ cells are produced only from the peritoneum of the genital region and their earliest formation is coincident with the thickening of the coelomic epithelium to form the genital ridge. This takes place eleven days after insemination in embryos of approximately 18 somites. Germ cells continue to form from the peritoneum during the early development of the gonad. The peritoneum of this region also produces mesenchyme, smaller cells of the gonads, and the germinal epithelium.The argument for the specific character of the germ cells in vertebrates and their continuity from the egg is based largely upon assumption, and not upon substantial observations, and must be discarded. Germ-cell origin is a problem of cellular differentiatio, and not of early segregation.
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  • 52
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Systems of fiber-like structures traverse ciliated cells and epithelia in a way to suggest conduction paths for stimuli for coordinating and regulating ciliary movement, and results of microdissection support such an interpretation.Some fibers of the systems in epithelia of the gill terminate on the nuclear membrane, some between nuclei in the basal cytoplasm.The observed double refringency of the fibrillar apparatus places it in the category of irritable and contractile substance.Bipolar cells and nerve-like fibers lie immediately below and parallel with ciliated epithelia of the gill, but direct connections of these fibers with the intracellular system, although suspected, was not demonstrated.Ciliated epithelia of the gill are syncytial in character in the direction of the beat of cilia.Interciliary structures occur in the cuticular portion of ciliated epithelia which are interpreted to function in taking up strains in the gelled cytoplasm caused by the beat of cilia.Cilia occur in pairs in epithelia of the gill, and members of pairs are fused at their distal ends.Each cilium, as seen in dark-field illumination, pierces its basal body, and the fiber that is a continuation of the cilium divides immediately below the basal body into two; one diverging to the right, one to the left.Each cilium is composed of many delicate fibrillae.
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    Journal of Morphology 40 (1925), S. 559-573 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: One of the most perfect “lock and key” adaptations known, the external reproductive organs in spiders are subject to considerable variations. Two extreme types of female reproductive organs are described in detail, and these in turn compared with the European species of the same genus. Thus it is shown that the reproductive system in the same genus of spiders may exhibit great differences in structure while all other characters remain more or less the same, the natural conclusion being that caution should be exercised in creating new or splitting up old genera on the basis of characters of the external reproductive system. The same applies to the male.Two extreme types of palpi are described and then compared with the palpi of the European species. In the case of the male, however, the differences seem to be of a less profound nature.
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 41 (1925) 
    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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  • 55
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    Journal of Morphology 40 (1925), S. 575-592 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The shedding of epidermis in this species, as in most amphibia, is periodic. A single outer layer of cells separates nearly simultaneously over the whole body; two hours to ten days may be required for the process. In the first three months of laboratory existence the average frequency of molting was 9 per cent. In nature the frequency was only 2 per cent; this increased during the life in confinement in five months up to 25 per cent. Death in the laboratory was usually preceded by numerous molts.The time of a molt is not normally determined by any one of a number of ordinary external conditions which were modified; but nevertheless several means were found of inducing molting. These were, in order of their efficacy: bandaging with gauze on body or tail, wrapping the body with thread, stitching the body wall, applying hot water, and transplanting skin. Molting frequencies up to 98 per cent may thus be obtained.Since molting is periodic and simultaneous, it is evidently coordinated. Experimental induction requires a latent period of six to ninety-six hours, depending upon the stimulus. Recent skin grafts molt with the host, so that the coordination is probably chemical. The primary significance of molting in all groups of animals is possibly the getting rid of unautolyzable waste materials, i.e., worn epithelial structures.
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  • 56
    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 of urodeles and anurans can occupy comparable positions in the embryo only in very early stages of development, if at all. When first recognizable as reproductive elements, their situation in the two amphibian orders is quite strikingly different.The germ cells first become recognizable in urodeles in the medial edge of the lateral mesoderm; there is no evidence that their position previous to this time is other than mesodermal. In the anura they are entodermal in association during early development; they are finally separated from the dorsal portion of the roof of the archenteron to form a single axial germ-cell cord. No amphibian species studied showed a mode of origin different from that characteristic of its order.The so-called migration of the amphibian germ cells to their definitive situation is interpreted as the result of growth shiftings of related parts. Germ cells do not migrate independently through the tissues. Aberrant or ectopic cells for the most part result from failures or faulty correlations of growth processes. Certain aberrant cells of the caudal portion of the body in urodeles indicate the inclusion of sex elements in the ventral as well as in the lateral mesoderm.
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  • 57
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The musculature of the ophidian head is a fairly complex structure, due to the specialization of the skull and the peculiar movements and motions made possible by the high degree of streptostylism.This musculature has been derived from the lacertilian type by a splitting and a shifting of the original elemental muscle masses of this group. Most of the muscles are clearly homologous with those of the Lacertilia. Some cannot be homologized by a study of the mature forms.The greatest differences lie in the separation of the muscle masses in the ophidia, as compared with the undivided masses in the Lacertilia. Since the jaw movements of the Lacertilia are rather simple, there is no need for any subdivision or splitting of the jaw muscles, but with the complex movements of the ophidia this becomes necessary.A few of the ophidian muscles appear to be neomorphs, as no key to their origin could be determined by a comparison with lacertilians.
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    Journal of Morphology 41 (1925), S. 191-216 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Painted turtles, gopher tortoises, and terrapins were fed on various mixtures of sand, salts, dextrin, casein, cod-liver oil, wheat, eggs, lettuce, and meal worms. Each individual was weighted weekly for about a year and then killed for analysis, the water, ash, nitrogen, and fat being determined. Some individuals increased in weight as much as 75 per cent, others lost weight. Judged by growth and chemical analyses, the food requirements of chelonians, as representative poikilothermal vertebrates toward nutritive substances (including vitamines) are similar to those of homoiothermal animals.
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  • 59
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of removal of the liver has been noted in fishes, frogs, and turtles. As in the higher vertebrates, removal of the liver produced a fall in blood sugar and a loss in muscular tone. The lower vertebrates failed to respond to intravenous injections of glucose, as do the birds and mammals. They also fail to respond to maltose or levulose. The liver maintained the blood-sugar level in the lower vertebrates, which is necessary for the maintenance of life.The mechanism of carbohydrate metabolism in the lower vertebrates may be different from that in the higher ones, in that glucose, when injected intravenously, apparently exercises a progressively less beneficial effect on the characteristic hypoglycemic condition which follows the removal of the liver of mammals and cold-blooded vertebrates.
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    Journal of Morphology 41 (1925), S. 217-237 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The female reproductive system comprises the ovaries, oviducts, vagina, spermatheca, and spermathecal gland. No colleterial glands are present. The ovaries are paired and each is composed of about eighteen ovarian tubules terminating in a cup-shaped modification of the oviduct - the egg calyx. The epithelial lining of the oviduct is glandular. The spermatheca, a bladder-shaped sac situated dorsal to and between the two ovaries, opens into the vagina near the exterior and is filled with spermatozoa after copulation. Spermatozoa have not been found in any other part of the female. Dorsal to the spermatheca and lying against it is the spermathecal gland. It is connected with the spermatheca by an elongate spermathecal duct.The male reproductive system comprises the testes, vas deferens, accessory glands, and the penis. Each testis is composed of eight to ten cone-shaped follicles, which are composed of a number of cysts so arranged as to appear segmented. All of the cells of each cyst are in approximately the same stage of development. No seminal receptacle is present. Each follicle is connected with the vas deferens by an efferent tube. The paired vas deferens opens into the sac-like intromittant organ or penis. The terminal portion of the penis may be everted, and when everted is conical in shape. At its base is a thin chitinous collar, the margins of which are thickened, forming ridges.
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