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  • Cell & Developmental Biology  (285)
  • 2000-2004
  • 1980-1984
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  • 1935-1939  (249)
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  • 1938  (125)
  • 1926  (36)
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  • 2000-2004
  • 1980-1984
  • 1965-1969
  • 1940-1944
  • 1935-1939  (249)
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  • 1
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The blood of Perophora viridis is found to contain six types of cells: (1) Green cells, which have green-colored fatty bodies embedded in clear cytoplasm. (2) Orange cells, with orange-colored bodies of unknown composition in the cytoplasm. (3) Colorless berry-like cells, with fluid-filled vesicles in the cytoplasm. (4) Granular amoeboid cells. (5) Compartmental amoeboid cells, which have box-like vacuoles containing brownian granules of a fatty substance. (6) Vesicular, signet-ring type of cell having a single large vacuole. The cytological structure of these cells and their reaction to various dyes are described.An effort has been made to homologize the types of cells found in the blood of other ascidians with those found in Perophora.It is concluded that the variety of colors found in the cells of ascidian blood is due to the varying chemical states of the vanadium-containing chromogen present in the cells.
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  • 2
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 42 (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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  • 3
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 42 (1926), S. 111-141 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    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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  • 4
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 42 (1926), S. 83-109 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The summary of this paper is as follows:1A critical review of the developmental evidence shows that the branchial pouches are formed in cephalocaudal sequence subsequently to the segmentation of the dorsal mesoderm.2The pouches interrupt a continuous sheet of mesoderm to form the branchial arches.3The arches when formed do not correspond topographically to the dorsal somites.4Branchiomerism does not therefore coincide with somitic metamerism.3The branchial structures do not support the theory of head segmentation.3The nervi trigeminus, facialis, glossopharyngeus, and vagus cannot be regarded as segmental nerves.3There is no evidence that branchial pouches or arches have been elided from the series.3The problem of meristic homology is briefly discussed.
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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: 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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  • 6
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the golden-mantled ground-squirrel, Callospermophilus, a spatulate glandular area has been noted in the skin of the back. It has been found in the following species: C. l. lateralis, C. l. arizonensis, C. l. caryi, C. l. saturatus, C. l. tescorum, C. c. chrysodeirus, and C. bernardinus. Probably it is common to the genus.The individual glands making up this area are modified and enlarged sudoriparous glands. They are divided into a tightly coiled and branched fundus, a large sinus, and a duct which passes caudad and outward to its exit at the surface.The glands secrete a strongly smelling oil, which is probably left on vegetation and other objects in the animal's environment and serves as a source of information to other members of the species. The glands are more active in spring and summer than in winter. They are stimulated by excitement. While present in both sexes, both adult and juvenile, they are best developed in adult males.Callospermophilus has three anal glands. These have flat-topped, straight-sided nipples which are protruded from the anus if the animal is frightened. A milky substance with a very weak odor can be extruded.
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  • 7
    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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  • 8
    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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  • 9
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    Journal of Morphology 41 (1926), S. 427-439 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    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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  • 10
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    Journal of Morphology 62 (1938), S. 91-111 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The clam Mya differs from other pelecypods which have been investigated in this respect in having most of the reserve nutritive materials formed within the vacuolated follicle cells of the gonads instead of within the very limited amount of mesenchymatous connective tissue of the visceral mass. The profusely branching tubular gonads originate from two groups of primordial germ cells situated in the position of the future genital apertures. The germinal primordia soon become differentiated into two types of nuclei, one of which becomes associated with the large, vacuolated follicle cells, which form the principal volume of the gonadal tissue, while the other type proliferates to form the primary gonia which become widely scattered along the walls of each alveolus.There is much degeneration and cytolysis during gametogenesis in both sexes, with the accumulation of characteristic inclusions within the follicle cells. Atypical spermatogenesis followed by cytolysis occurs throughout the year but the normal method only in preparation for spawning. No evidence of protandry or change of sex was obtained; only three hermaphrodites were found in the examination of more than 1000 individuals.
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  • 11
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    Journal of Morphology 62 (1938), S. 1-2 
    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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  • 12
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The regeneration of muscle in larval Amblystoma punctatum is preceded by an extensive dedifferentiation of the old muscles of the limb stump. The process of muscle dedifferentiation consists in a separation of muscle nuclei, surrounded by a small amount of cytoplasm, from the injured ends of the muscle fibers. The dedifferentiation of the cut muscles of the limb stump progresses proximad as far as the origin of the muscles on the humerus and results in a complete transformation of these muscles into undifferentiated cells which appear to contribute to the formation of the regeneration blastema. Shoulder muscles, which were attached to the humerus, also undergo a partial dedifferentiation when their points of insertion on the humerus are destroyed by the degeneration of the perichondrium. These muscles never dedifferentiate, however, for more than one-fourth their original length. The process of dedifferentiation in the shoulder muscles is similar to that found in the cut muscles of the limb stump.The regeneration of the injured muscles occurs in two ways. The shoulder muscles reconstitute themselves by means of terminal and lateral sarcoplasmic buds formed near the distal regions of the muscle fibers. The muscles of the limb proper, distal to the shoulder, differentiate out of local aggregations of blastema cells. No myoblasts were observed.The regeneration blastema arose chiefly from dedifferentiated cells of muscle, nerve connective tissue sheath, perichondrium and cartilage.
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  • 13
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    Journal of Morphology 62 (1938) 
    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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    Journal of Morphology 62 (1938), S. 177-218 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The original innominate bone consisted of ischiopubis only. From this developed a dorsally-directed ilium, upon which the dorsal limb muscles, originally arising from fascia, settled, and which thrust dorsalward between roots of the limb plexus, thus dividing the nerves into prozonal (dorsal and ventral) and metazonal (dorsal and ventral) groups. The primitive muscles of the tetrapod hip and thigh comprised a dorsal mass, soon divisible into sheets, innervated by both prozonal and metazonal dorsal nerves, and a similar ventral mass comparably innervated. The original two elements thus became four basic elements, and probably in early mammals or mammal-like reptiles all dually innervated muscles split into singly innervated units. With this four-group basis as the chief criterion, but considering other factors as well, it is possible to homologize the muscles of urodeles (ventral components only), lacertilians, mammals, and birds in entirely satisfactory manner, except for doubt in several instances in which specialization has secondarily obscured the precise relationships. In different mammals there is shown a tendency toward a final fusion of certain unrelated muscle units (biceps plus gluteus longus, human type of biceps, adductor magnus, and tensor fasciae femoris with gluteus maximus).
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  • 15
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 62 (1938) 
    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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  • 16
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    Journal of Morphology 62 (1938), S. 415-443 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the blastula stage the roof of the subgerminal cavity is composed of an irregular layer of cells, the nuclei of which lie in the upper or middle part of the cytoplasm.On the floor of the subgerminal cavity groups of already degenerating cells occur. They represent the vegetative pole of the blastula. Almost every cell contains glycogen, and mitotic cells show no special orientation.In the gastrula stage the cells of the area pellucida become regularly arranged as a single-layered, cylindrical epithelium with basally situated nuclei.The yolk endoderm cells are formed from the proliferating upper layer of the area opaca.The embryonic endoderm is formed at the posterior end of the area pellucida by outgrowth of single cells from a circumscribed area, the primitive plate.This plate eventually bends inward to form a typical archenteric canal, through which endoderm continues to invaginate from the epiblast.The endoderm spreads in a cranial and lateral direction until it has formed a complete layer.The epiblast cells lose their glycogen as they invaginate to form endoderm, which is free of glycogen.In the area opaca the upper layer and the yolk endoderm contain glycogen.The mitotic cells of the epiblast of the area pellucida are always orientated horizontally, but in the primitive plate and archenteric canal they are orientated vertically as well.
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  • 17
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    Journal of Morphology 62 (1938), S. 559-597 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The larval, metamorphosing and definitive aortic arches of Desmognathus fuscus, Plethodon cinereus, Eurycea bislineata, and Gyrinophilus porphyriticus, described in this paper, were investigated because it was thought possible that, if the fourth or pulmonary arch failed to develop in these lungless forms, a new factor associated with the loss of lungs might be revealed.The salient points of structure disclosed, so far as the problem involved is concerned, are: D. fuscus and P. cinereus develop fourth arches which remain functional in the larvae and adults and supply the pharynx, oesophagus, stomach and skin of the shoulder region. In some instances the fourth arch in the larvae of P. cinereus is reduced in length or entirely lacking in which cases correspondingly less of the fourth arch and more of the third arch is present in the adult. E. bislineata and undoubtedly G. porphyriticus fail to develop fourth arches and hence do not possess these in either the larval or adult states.It is concluded, therefore, that the failure of the fourth arch to develop has evidently not been a factor involved in the advent of lunglessness in plethodontid salamanders. Also, the fact that E. bislineata never develops a fourth arch, yet is able to transform, furnishes additional evidence against Figge's view that Necturus fails to metamorphose because the ventral portion of the fourth arch is absent.
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  • 18
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    Journal of Morphology 63 (1938) 
    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
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    Journal of Morphology 63 (1938), S. 75-86 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study is based on serial sections of the occipital and otic regions of a therocephalian from the Tapinocephalus zone. The occipital region as preserved consists of the basioccipitals and exoccipitals. The basioccipital is long and slender and is separated from the more anterior basisphenoid by an unossified zone. The exoccipitals are large and contain a part of the jugular foramen and two foramina for cranial nerve XII.The otic bones are fused together to form a periotic. The most striking feature of the inner ear is the medioventral position of the vestibule. Passing back into the periotic from the vestibule is a deep recessus scala tympani. This recess opens anteriorly into a ventral fenestra in the vestibule, the fenestra rotunda. These structures are similar to those of Dimetrodon and the gorgonopsian.The anterior part of the periotic is projected ventrally to form a basicranial process. This probably arose by intramembranous ossification. The unossified zone between the basioccipital and basisphenoid may represent a persistent basicranial fenestra.
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  • 20
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    Journal of Morphology 63 (1938), S. 63-73 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A study has been made of the growth of the eye anlage, and of the increase in number of the elements of the dioptric system of larvae of Drosophila melanogaster.In newly hatched larvae the eye rudiment grows fast, but slows down later and becomes nearly stationary during the second half of larval life. The increase in number of elements in the eye disc parallels the growth of the whole anlage and reaches a maximum about 70 hours after hatching. The imaginal disc cells increase in number but not in size, in contrast to other larval cells which increase in size but not in number.
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  • 21
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    Journal of Morphology 63 (1938), S. 87-117 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The form of the vertebral column is definitely related to its function as a supporting rod, a base for attachment of body and limb muscles, and a protection of the spinal cord and nerves. Primitively composed of a series of simple undifferentiated blocks, it progressively becomes complicated through development of articular processes giving added strength and greater mobility. Simultaneously, the centrum and the neural arch become adapted to withstand tension and compression stresses which vary with the movements possible in different regions of the column. These movements are partially determined by the plane of the zygapophyses and the nature of the intercentral articulation, together with the action of the axial muscles and ligaments.In fish and primitive tetrapods the axial musculature serves as the chief locomotor organ and consists of a series of myomeres extending with little interruption from the head to the tail. In tetrapods the locomotor function is taken over by the limbs and the axial muscles become progressively differentiated into long flexors and extensors of the column and gradually lose their external segmentation.
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  • 22
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Adult salamanders of Ambystoma tigrinum show a high degree of sexual dimorphism. The normal growth of the urogenital ducts system in relation to the development of the gonads is traced from the sexually indifferent period preceding metamorphosis to sexual maturity at 1 year. Differentiation and growth of secondary sex characters is correlated with spermatogenesis in the male and with growth of ovocytes in the female.Testicular hormone manifests its initial appearance in male differentiation of the wolffian and urinary collecting ducts following metamorphosis. Growth of ovocytes and oviducts begins before metamorphosis and may be assumed to indicate the initial appearance of the ovarian hormone. Females retain the larval arrangement of wolffian and urinary ducts. The oviducts of the male regress during the period of rapid male differentiation. This suggests the possibility of antagonistic activity of the male hormones in Ambystoma.
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  • 23
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    Journal of Morphology 63 (1938), S. 143-161 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A batch of fifty newts was subjected to complete food deprivation for a period of 4 months. During the experiment twenty-two individuals died and twenty-eight were killed at intervals. From the end of the second month the erythrocytes began to show in increasingly greater numbers a progressive alteration in the nucleo-cytoplasmic ratio. The nucleus of these atypical erythrocytes gradually enlarged and ultimately occupied the entire cytosome. Meanwhile the nuclear reticulum became extremely fine and closely meshed, eventually appearing practically homogeneous and relatively chromophobic. The end result was complete dissolution. The leukocytes became greatly reduced in number, the eosinophils disappearing completely. The neutrophils and basophils were agranular in the blood smears. The erythrocyte transformations represent late results of a chain of factors: cytoplasmic hypotonicity, nuclear endosmosis, attenuation and fenestration of nuclear membrane. The subcapsular lymphogranulocytopoietic tissue of the liver had almost completely disappeared. The spleen was greatly reduced in size; it was essentially lymphoid in character and erythrocytopoietic activity had ceased practically completely. Complete restoration of normal conditions in blood, liver and spleen was effected by the end of 2 weeks by feeding with earthworms. The regenerating blood showed many naked nuclei of disintegrating atypical erythrocytes, many immature erythrocytes in mitosis, increased number of small lymphocytes (lymphoid hemoblasts), large but variable numbers of microcytes, many giant thrombocytes and normal granulocytes.
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  • 24
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Colloidal carbon injected into the coelom of the larval lamprey, Ammocoetes, is taken up directly by the pronephric tubules. Due to the absence of nephrostomes the mesonephric tubules do not function in a similar way. The tubules of neither show any intracellular deposition of carbon. The reticular elements which support both these kidneys exhibit pronounced phagocytic and hemocytopoietic activity. Carbon in either a free or included form reaches all the other organs both as a result of direct invasion or secondary distribution by the vascular system. The liver is the only organ whose vascular endothelium exhibits cytopoietic properties. To the diffuse spleen as a site of blood cell formation thus should be added the reticular tissue of the pronephros and mesonephros and the vascular endothelium of the liver. Playing a minor role in a similar way are the intestinal mucosa exclusive of that in the typhlosole and the spongy tissue dorsal to the neural tube.
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  • 25
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    Journal of Morphology 63 (1938) 
    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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  • 26
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    Journal of Morphology 63 (1938), S. 181-205 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In an earlier paper (Slifer, '37) experiments were reported which showed that in Melanoplus differentialis eggs the hatching enzyme, which destroys the white cuticle, is secreted by the pleuropodia (appendages of the first abdominal segment of the embryo) during the last few days of incubation. In the present report the development and differentiation of the pleuropodia, together with the cytological changes which occur in them before, during and after they become functional, have been followed. The time at which the secretion granules are discharged from the pleuropodial cells was found to be closely correlated with the time at which the tough, white cuticle begins to disintegrate. The cytological evidence, then, supports the author's earlier conclusion, based upon experimental work, that the pleuropodia secrete the hatching enzyme.
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  • 27
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    Journal of Morphology 63 (1938), S. 207-217 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Comparison of intramembral and trunk/limb proportions in the roadrunner (Geococcyx) and two related genera of cuckoos (Coccyzus and Crotophaga), together with a consideration of their habits of locomotion, lead to the following two generalizations: (1) The incipient cursorial leg of more primitive, arboreal birds, with the metatarsus shorter than the femur, is not an efficient mechanism for bipedal terrestrial locomotion. The direct adaptation to the cursorial habit in terrestrial birds lies in the further elongation of the whole leg, the distal segments undergoing a relatively greater elongation than the femur; the greatest degree of elongation is shown by the most distal segment. (2) When the development of terrestrial, cursorial habits in birds leads to diminished use, or discuse, of the wings as organs of locomotion, the wing skeleton becomes reduced in length; each segment of the wing is reduced, but the degree of reduction is greatest in the more distal segments. It is probable that reduction appears first in the most distal segment and later successively in each segment proceeding proximally therefrom.
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  • 28
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    Journal of Morphology 63 (1938), S. 219-227 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The median cord arises as a hypodermal invagination along the midline from stomodeum to end of tenth abdominal ganglion. It separates from the hypoderm, but does not differentiate into any tissue; apparently it degenerates.
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    Notes: There are 19 chromosomes in diploid cells of male Paratylotropidia brunneri; of these, four are V-shaped multiples. There are twenty chromosomes in diploid cells of females; of these, four are V-shaped multiples. If the two arms of each multiple are counted as separate chromosomes, we have the usual number of chromosomes for the Acrididae, i.e., twenty-three in male and twenty-four in female.There are nine chromosomes in the first spermatocyte divisions: seven tetrads, one octad and a decad. The latter is made up of the accessory chromosome associated with an octad.One of the V-shaped multiples in the male is limited to that sex. The homologue of one of the dyads of which it is composed is a free dyad, the homologue of the other forms a V-shaped multiple with the accessory chromosome. The V-shaped multiple limited to the male shows differential heteropycosis in the prophases of the first spermatocyte. There is evidence that its homologous parts are isolated from each other as far as crossingover is concerned.A study of the first maturation division of the heterogametic sex is essential for the identification of the sex chromosome.
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  • 30
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    Journal of Morphology 63 (1938), S. 229-261 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Although thoracic diverticula of the aorta ending dorsally in pulsatile organs were discovered by Brocher as early as 1917 no detailed account of their structure was published. The condition of these structures in the adult was not investigated and their development through larval instars was not followed. Brocher's later papers announced the discovery of similar organs in the orders Orthoptera, Coleoptera and Lepidoptera. In 1931 E. Meyer described in some detail pulsatile organs in the Ephemerida. In general these accounts are either superficial or of doubtful interpretation.The present paper deals with the Odonata and stresses the Anisoptera. Anax junius has been studied as the type both anatomically and histologically in all stages of larva and imago except the first four instars. Other types have been compared with Anax, and some of the other orders mentioned have been checked for presence and nature of these organs.Aortic diverticula and pulsatile organs occur in all Odonata both larval and adult. These are derived from the same origins and their histology is that of the membranes involved in aortic and body walls. Through inference from morphology and from physiological examination it appears that pulsatile organs (1) supplement heart action, perhaps substituting for it during emergence. (2) assist in the functioning of the ostia and ostial glands, and (3) may even be important in production and distribution of hormones.
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  • 31
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The germinal epithelium was studied in an effort to determine its role in postpubertal ovogenesis. Active and inactive areas of epithelium were observed regardless of the oestrous periods. The active areas, exemplified by numerous mitoses and a frequent stratification of the epithelium, are foci for egg cell production.Egg cells are produced from the germinal epithelium by: activation, migration and transformation of single germinal epithelial cells; migration and differentiation of nests of cells; ingrowths of cords of cells.Young ova in the cortex of the ovary are at first surrounded by a single layer of flattened follicular cells of germinal epithelial origin. In the subsequent development of the follicle stratified layers make their appearance. The zona pellucida appears as a well-defined structure coincident with the stratification of the follicular layers.The follicular cavity develops as a split between the follicular cells at one side of the follicle. In the mature follicle the cavity is broad and contains liquor folliculi. The theca interna and externa are not distinguishable until the follicle is highly cellular.
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  • 32
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    Notes: The spermatogenetic cycle of the testis of the musk turtle is limited to the summer months of the year, and closely parallels that of the anuran Amphibia. Spermatozoa are present in the testis from September to May, and breeding may occur in either fall or spring. A pronounced increase in the size of the epididymis and a corresponding decrease in the size of the testis occurs at the end of the cycle (September).During the months of March, April and May, all spermatozoa are eliminated from the seminal tubules, and the germinal epithelium is built up in preparation for spermatogenesis. Spermatogonial divisions occur in small numbers in May, and the division tempo increases during June. Primary spermatocytes and maturation divisions appear after the middle of June, and continue through July and August. Spermiogenesis begins in late July, is in full progress in August, and is practically completed by October. Laboratory specimens usually show an active spermatogenesis in winter, but it is not probable that a second spermatogenetic cycle occurs in specimens under normal hibernating conditions.No seasonal changes are observed in the interstitial cells of the testis, and no seasonally variable secondary sex characters are known for turtles. Special studies of the problem are being conducted.
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  • 33
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    Journal of Morphology 63 (1938), S. 345-361 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This species represents a typical example of protandric consecutive sexuality, the male phase becoming functional at a very early age, when the body has reached a length of only 3 to 7 mm. Those males which become functional earliest usually seek the association of older individuals in the female phase; others, maturing later, are more likely to remain solitary. Mated males have accentuated masculine characteristics and retain the male phase longer than solitary individuals or those that are isolated experimentally. Unfavorable environmental conditions postpone or prevent functional sexuality and terminate the male phase promptly without inaugurating the female phase. The influence of the female in accentuating the sexuality of the male is thought to be due to stimuli received by the latter through sense organs in tentacles and penis and mediated by the nervous system through hormonal secretions. Termination of the male phase and transition to the functional female are comparable to metamorphosis from the immature to the mature condition in other animals and, like metamorphosis, the primary (male) sexual phase can be abbreviated or prolonged experimentally, but the sequence cannot be reversed.
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  • 34
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    Notes: Data concerning the seasonal distribution of twenty-two species of nudibranchs are recorded for a period of 9 months. The occurrence of copulation and of egg laying for these animals in the laboratory aquaria is recorded for the same period. These data indicate that the seasonal distribution of certain species is well marked, and that there is in many cases a definite breeding season.The characteristics of the egg ribbons of these nudibranchs are described, and figured by means of photographs. These egg ribbons approach the mathematical form of a spiral of Archimedes. In every case observed, the ribbon was deposited in a counter-clockwise direction, viewed dorsally.The relationship between these observations and earlier work on the life histories of the nudibranchs is discussed.
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  • 35
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    Notes: Salivary gland nuclei in Chironomus regularly show large, conspicuous nucleoli. In Sciara no true nucleoli have been found, but sometimes certain particular chromosome regions expand greatly, forming ‘puffs’ or ‘bulbs,’ somewhat nucleolus-like in nature. Detailed study has been made of the chromosome structure in the affected regions in both genera.In the nucleolar regions of Chironomus the banded structure of the chromosome is distinctly modified. In the case of the large nucleolus the chromosome breaks up into a heavy network in which solid discs are replaced by interconnected chromatic spheres and granules, extending out somewhat into the clear nucleolar substance. In the case of the smaller nucleolus, Balbiani's ring, the banded structure is less disturbed. A chromatic network, resembling a system of rootlets, runs out from the chromatic bands into the clear nucleolar substance.In Sciara ocellaris the ‘puff’ regions are at times normally banded, but at other times in the condition described as ‘puffed.’ The same is true of the ‘bulb’ regions. The relation between nucleoli, puffs and bulbs is discussed. Also that between ‘heterochromatin’ and ‘euchromatin.’ Evidence seems to indicate that the latter are merely extremes in a continuous range involving different relative amounts of chromatic and achromatic materials. The ‘puff’ regions appear to be structurally similar to the chromocenter in Drosophila.
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  • 36
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    Journal of Morphology 63 (1938) 
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  • 37
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    Journal of Morphology 63 (1938), S. 397-419 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The summary of this paper is as follows:1From an examination of 108 ovaries from eighty-nine individuals it was apparent that, in the cat a certain but variable amount of degeneration of primary follicles occurs in all life epochs.2The primary oocytes undergo the degeneration, while the follicle cells remain for an undetermined time.3The most profound instances of such degeneration were encountered in kittens of 6 to 9 weeks, accompanying or follwing the resolution of the egg cords into primary follicles and the establishment of the cortical or marginal zone. A sporadic degeneration of young oocytes occurs at earlier periods.4No evidence was seen of a new formation of egg cells from the residual follicle cells after the degeneration of the oocytes. The degenerations of the 6 to 9 weeks epoch are not believed to be of universal occurrence.5No adequate evidence was encountered of a new formation of egg cells from the surface epithelium, either before or after sexual maturity.6No evidence linking the degeneration of primary follicles with the estrous cycle was seen.7The stock of primary follicles established in the first few weeks after birth is believed to be adequate for the growth of graafian.
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  • 38
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    Journal of Morphology 63 (1938), S. 421-439 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The maturation of the germ cells of the two hermaphroditic species, Curtisia foremanii (Girard) and Bdelloura candida (Girard) has supplied the material for this chromosome study.Both species of flatworms are believed by the author to possess a diploid number of twelve chromosomes and a haploid number of six, although Curtisia foremanii has previously been reported as having a smaller and variable number of chromosomes.A tendency of the chromatids comprising individual chromosomes to separate from one another at certain times was noted in both species. This action results in giving the appearance of a larger number of chromosomes than the germ cells actually possess. A further source of apparent increase in chromosome number in the Curtisia oocytes, after treatment with the usual Allen's B3 and B15 and Heidenhain's iron haematoxylin, is the presence of some deeply staining, non-chromatin material.No significant differences in number, form and behavior of chromosomes of male and female complexes were noted, with the possible exception of the tendency of the chromatids to separate from one another, to be greater in the female than in male germ cells.
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  • 39
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    Journal of Morphology 63 (1938), S. 441-475 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: Four cases of gynandry in American spiders present the following morphologic deviations: The specimen belonging to Neoantistea agilis (Keyserling) externally is a bilateral gynandromorph with distortion of the single male palp, with half of the epigynum nearly normal; internally both testes and ovaries are present. The Drassodes neglectus (Keyserling) is not a completely developed bilateral gynandromorph. One side has a normal male palp, a larger chelicera and longer legs than the other, the epigynum is complete and normal; internally only degenerate ovaries are present. The Linyphiid, near Bathyphantes, is three-quarters female, the only male organ being an imperfectly developed male palp. Ovaries are well developed but immature, whereas the epigynum is complete. In the Pardosa sternalis (Thorell) the anterior part of the body is male, as indicated by the swollen palps and the length of the legs; the epigynum is completely developed, but internal reproductive organs are missing except for a very much aborted ovary. The bisexuality in all cases has caused degeneration or abnormalities in the reproductive structures.Included is a tabulation of all recorded instances of gynandry in spiders, arranged according to the type of abnormality. The term ‘leg-index’ is introduced to express ratio between length of the leg and length of cephalothorax.
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  • 40
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    Notes: Centrifuging the eggs of Rana pipiens in the early gastrula stage prevents the formation of the hypophysis in some of the tadpoles. The absence of the melanophorotropic hormone normally secreted by the hypophysis seems to be responsible for the contraction of the pigment cells. In addition, there are actually fewer pigment cells present in both the dermal and epidermal layers of the light tadpoles than there are in the controls. The paleness, therefore, of the tadpoles seems to be due to both a contraction of the pigment cells present and to an actual reduction in their number. The failure of the hypophysis to develop was brought about by centrifuging at an earlier stage in development of the embryo than in previous extirpation studies. The effects produced by centrifuging that are responsible for the failure of the hypophysis to develop are unknown. However, it is suggested that interference in some way with the presumptive hypophysis-forming tissue has resulted in an inactivation of its inductive potencies.
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    Journal of Morphology 64 (1939) 
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  • 42
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    Journal of Morphology 63 (1938), S. 491-529 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: This paper is based on evidence obtained from sectioned skull of Galesaurus planiceps, Owen. Width-length index of skull is 67.7; height-width index 47.6. Dental formula is: \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{{\rm I\; 3\; or\; 4}}}{{{\rm I\; ?}}} $\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{{\rm C\; 1}}}{{{\rm C\; 1}}} $\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{{\rm PC\; 7}}}{{{\rm PC\; 9}}} $\end{document}. Length of prevomer is 24.0 mm., that of skull 62.0 mm. Maxilla contains cavity which appears to be equivalen of sinus maxillaris of mammals. Ear structure shows large internal auditory meatus. There is no evidence that horizontal and posterior semicircular canals pass through bone. Fenestra ovalis is large. Parasphenoid, basisphenoid, and basioccipital are fused. Parasphenoid consists of short body and a medial anterior process. Sella turcica lacks floor, probably due to erosion. Detached bone may be sphenethmoid. Dentary contains two canals, probably vascular. Comparisons with related forms lead to following conclusions: (1) Specimen is of young animal. (2) Dental succession of postcanines, distichical replacement of postcanines, long prevomer, short parasphenoid, incomplete osseous incasement of semicircular canals, and other characteristics label Galesaurus as primitive cynodont. (3) Reduction of parasphenoid and development of prevomer support Broom's view that Ictidosaurus is not a cynodont. (4) Prevomer as nasal septum; fusion of parasphenoid, basisphenoid, and basioccipital; large lacrimal, splenial, and articular; and other characteristics indicate that Galesaurus is off line leading to mammals. (5) In certain respects cynodonts are more mammal-like than gorgonopsians.
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  • 43
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    Notes: The development of the cranial musculature of Amblystoma punctatum is described in detail, for both larva and adult. In addition, a brief account of the innervation of each muscle is given. The study of normal development is supplemented by extirpation experiments performed on embryos in early stages of development. These extirpations include the mesodermal head segments, mesoderm of mandibular, hyoid, second branchial, third branchial arches, and somites 1, 2 and 3. The eye muscles are found to develop from the mesodermal head segments in precisely the same manner as in other classes of vertebrates; head segmentation of Amphibia, though less accentuated, is shown to be homologous with that of other classes. The remaining extirpation experiments corroborate, in general, the finding from normal development studies. An attempt is made to summarize in tabular form the prospective fate of the prechordal plate and parachordal mesoderm, the two earliest divisions of the head mesoderm, with regard to their complete muscle derivatives.
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  • 44
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    Journal of Morphology 64 (1939), S. 1-8 
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    Notes: A law of the “bi-triangular medial concentration of the cephalic appendages” in the Chilopoda and the Insecta is propounded. According to it, the cephalic appendages lying in front of and behind the intercalary pair of appendages undergo a concentration, both in phylogeny and in ontogeny, toward the median line. In this way, two hypothetical triangles, termed the ‘anterior or procephalic triangle’ and the ‘posterior or gnathocephalic triangle’ are formed, having a common base in the level of the intercalary appendages. The cephalic appendages occupy roughly either the sides or the apices of the triangles and the degree of their final medial concentration is in direct proportion to their distance from the triangular base. Before the final bi-triangular condition is achieved by the appendages, varying types of transitory shiftings are passed through.
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    Journal of Morphology 64 (1939), S. 37-46 
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    Notes: 1. The prostomial glands, as described by Bourne, are deep-lying and unicellular, are distinctly different from the salivary glands, and their contents do not stain with boraxcarmine. They are ectodermal in origin.2. The material for the cocoon is secreted by the clitellar glands, while the prostomial glands secrete the yellowish plugs at the two poles which close the two ends of the cocoon.3. A fortnight after the cocoons are formed, the plugs become detached, leaving two outlets one at each pole, for the young leeches to wriggle out of the cocoon.4. The detachable plugs are possible only if not made of the same material as the cocoon.
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    Journal of Morphology 64 (1939), S. 9-35 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the hepatic cells of well-fed salamanders (Triturus pyrrhogaster) elongated mitochondria predominate which exhibit a diversity of shapes. Starvation tends gradually to produce a shift in predominance from the elongated to the granular forms of mitochondria; terminally looped and ring-shaped mitochondria also characteristic of the well-fed condition, gradually become rare to absent. Beaded elongated mitochondria increase in number after short periods of fasting, and appear to be transitional between smooth elongated mitochondria and granular mitochondria.Re-feeding tends to bring about a recovery of the mitochondrial picture of the well-fed animals.There are exceptions to the above general trend which show that the length of starvation and digestive activity are not the only factors that account for the changes in the mitochondrial condition. A closer relation is found between the mitochondrial condition and the relative amounts of fat and glycogen in the cell. It can be stated as a rule that the shift in predominance from elongated mitochondria to granular mitochondria parallels the decrease in amount of fat and glycogen in the cell.
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    Journal of Morphology 64 (1939), S. 47-66 
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    Notes: Glands are classified by structure as multicellular complex acinose, multicellular simple tubular, and unicellular; by position as general, hypodermal, ocular, anternnal, intra-mandibular, mandibular, mandibulo-maxillary, maxillary, intra-cardonal and labial. Some open outside the extra-oral cavity. They are supposed to be offensive in function. The segmental origin of the gnathial is doubtful.
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    Journal of Morphology 64 (1939), S. 67-87 
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    Notes: In Didelphis virginiana and Marmosa mexicana the retina is sauropsidan in type and the eye as a whole is markedly adapted for scotopic vision. The superior half of the fundus of Didelphis is occupied by a tapetum lucidum of the retinal type, formed by the enlarged pigment epithelial cells which are devoid of pigment and packed with reflective particles of unknown composition. Such a tapetum is unique among mammals - in all known sub-mammalian retinal tapeta the reflective material is guanin and is occusible in bright light by migratory fuscin. The retinal capillaries in Didelphis extend to the external limiting membrane, apparently in adaptation to the low permeability of the dense tapetum. Only four other mammals are known to have such capillaries and no inclusive explanation seems to hold for all. Didelphis possesses an ‘area centralis of sensitivity’ associated with the tapetum. Both genera have abundant rods and scanty cones, of three types. The oil droplets of the droplet-bearing single cones and the double cones are colorless and the double cone contains only one, not two as reported by O'Day for other marsupials; nor are the members of the double cone ever alike in size and form. Opossum double cones are thus perfectly orthodox; primitive placental mammals should be examined for double cones and oil droplets.
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    Journal of Morphology 64 (1939), S. 89-113 
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    Notes: Study of the epidermis of Rana pipiens and Amblystoma jeffersonianum showed no variations in the mitotic rate that were correlated with the age expressed in hours after hatching or with the time of day at which the tadpoles were fixed. The average mitotic index of the epidermis during the first day of larval life was 1.88 in the frog and 1.02 in the salamander. This was correlated with the earlier developmental stage at which the frog hatched. Colchicine in concentrations above 5 × 10-4 M. in the frog and above 2.5 × 10-3 M. in the salamander arrested almost all mitoses at metaphase. Inhibition was incomplete after treatment with concentrations of 1.25 × 10-4 M. in the frog and 5 × 10-4 M. in the salamander. Severe injury was characterized by the presence of vacuolated cells with deeply stained inclusions, similar to cells found after x-radiation. Cells continued to enter the prophase at the normal rate. The accumulation of metaphases during the first 4 hours of colchicine treatment indicated a mitotic period of about 80 minutes in the frog. During subsequent periods the expected accumulation of metaphases did not occur. It was concluded that the arrested metaphases either degenerated or passed into a resting stage without passing through anaphase.
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    Journal of Morphology 64 (1939), S. 167-209 
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    Journal of Morphology 64 (1939), S. 355-373 
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    Journal of Morphology 64 (1939), S. 375-399 
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    Journal of Morphology 65 (1939) 
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    Journal of Morphology 64 (1939), S. 519-553 
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    Journal of Morphology 65 (1939), S. 1-15 
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    Journal of Morphology 65 (1939), S. 17-51 
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    Journal of Morphology 65 (1939), S. 53-78 
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    Journal of Morphology 65 (1939), S. 79-119 
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    Journal of Morphology 65 (1939), S. 121-153 
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    Journal of Morphology 65 (1939), S. 187-213 
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    Journal of Morphology 65 (1939), S. 257-295 
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    Journal of Morphology 65 (1939), S. 241-255 
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    Journal of Morphology 65 (1939), S. 297-321 
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    Journal of Morphology 65 (1939), S. 323-351 
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    Journal of Morphology 65 (1939), S. 383-409 
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    Journal of Morphology 65 (1939), S. 437-469 
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    Journal of Morphology 65 (1939), S. 411-435 
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    Journal of Morphology 65 (1939), S. 471-495 
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    Journal of Morphology 65 (1939), S. 549-605 
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    Journal of Morphology 41 (1926), S. 441-546 
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    Notes: Embryological study of bullfrog tadpoles collected from various parts of the United States has shown the existence of local races which differ markedly in regard to the time of occurrence and character of the developmental processes involved in the formation of the definitive testis of the male individuals. Those races in which the gonads of the two sexes are easily distinguished in early larval stages are called differentiated. Other local races show a peculiar gonadic development chiefly affecting the males, the definitive testis sometimes not appearing until near the end of the second year of larval life. Such races are called undifferentiated, because the morphological features of the definitive testes are not established until late. The larvae first develop a peculiar gonad (progonad) which later degenerates and is replaced by the definitive testis. All male animals of the undifferentiated strains exhibit the gonad cycle.The progonad varies among the local frog races in regard to the length of persistence and degree of differentiation attained before undergoing degeneration. Its germ cells may exhibit a typical male maturation cycle ending in degeneration, or the cells may differentiate along both male and female lines or remain sexually neutral.The development and differentiation of the progonad in the various races are described and a detailed account given of the origin of the definitive testis. The problems of sex differentiation and continuity of the Keimbahn in anurans are discussed.
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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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    Journal of Morphology 41 (1926), S. 547-579 
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    Notes: The pelvic fins of the ancestors of the Chondrosteoidei possessed a metameric musculature and their skeleton consisted of a large number of metamerically arranged cartilaginous fin-rays, to which were attached osseous lepidotrichia. Evolution has involved the concrescence of separate elements to form the basal cartilage, the proximal end of which forms the girdle of the fin; the loss of a number of the fin-rays, and the atrophy of distal elements of the rays. The adult Chondrosteoidei have retained the primitive fin structure which characterized the elasmobranchs of the Palaeozoic period and which has disappeared in recent forms.
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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: Sixteen species of the genus Scyllium are here considered and arranged in groups according to the accessory structures present on the claspers as follows:1Canicula, sufflans, ventriosum.2Catulus, stellare, capense, variegatum (var. pantherinus), umbratile.3Burgerii, hispida, bivium, anale, natalense, edwardsii.4Marmoratum, laticeps.The structure of the wall of the oviduct and vagina is demonstrated, and it is shown that the epithelium of both is at first columnar, then ciliated in immature specimens; at maturity that of the vagina further undergoes by transitions a change to stratified. The walls are highly vascular, but contain no special glands.
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    Notes: Amoeba responds to a mechanical shock by a cessation of movement which occurs shortly after the application of the stimulus. The length of the reaction time, the period intervening between application of stimulus and the response, varies inversely with the magnitude of the shock. After stopping Amoeba remains quiescent for a short time, and the length of this period of quiescence varies directly with the magnitude of the shock. A certain amount of time must elapse after a reaction before another can be obtained; during this time the animal reverts to the physiological state which existed prior to the first shock.Partial recovery from the effects of a shock is manifested by a reaction time that is longer than after complete recovery, and a period of quiescence which is shorter. A shock which in itself is too slight to cause a cessation of movement may result in the lack of a response to a heavier one which follows immediately after it, although under other conditions the second shock would have called forth a reaction. If the second shock, however, is made sufficiently heavy, it will bring about a response, despite the effects of the first. This is what would be expected if the reactions take place in accordance with the Weber-Foechner law.
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    Journal of Morphology 42 (1926), S. 523-560 
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    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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    Notes: The lips of the animal are modified in relation to the act of passing seeds into the sac. The cheek-sacs are invaginations of the buccal mucosa, and their development as diverticula of the vestibulum oris is associated with the establishment of extrinsic muscles, derived from the platysma. The sac is invested by a coat of striated muscle. The epithelial lining of the sac attains a degree of complexity comparable to the epidermis of the skin, except that a stratum lucidum and stratum granulosum are not developed. No glands are developed in the mucous membrane of the sac.
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    Notes: Three groups of pure lines of diverse clones of Didinium nasutum were maintained in isolation cultures for 778, 786, and 457 generations, respectively, without exhibiting any decrease in fission rate or any increase in encystment rate or death rate. These lines were supplied with Paramecium caudatum in such numbers that a surplus of food was present at all times.Three other groups of lines of the same clones were established simultaneously and cultured in parallel with the preceding groups, but the food of each of these lines was limited to nine paramecia per line daily. The fission rate of these lines fell to zero and the encystment rate increased to 100 per cent after 155, 165, and 113 generations of culture, respectively. The death rate increased appreciably in these lines prior to encystment.Other groups of pure lines were cultured on a diet limited to six paramecia per line daily. These lines encysted after approximately fifteen generations of culture.This evidence indicates that there is nothing in the nature of a definite life-cycle in Didinium and that diminished vitality and encystment do not result from the passage of generations, but from inadequate and unfavorable cultural conditions-specifically, from in-sufficient food. It shows further that it is possible to induce cycles with reference to encystment in Didinium by limiting the food supply and to vary the length of the cycles by varying the quantity of food.
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  • 97
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    Notes: Chlamydoselachus resembles the Holocephali in possessing no siphon, but a cavity in the proximal portion of the clasper. The cartilages, musculature, and venous sinuses of the clasper are considered. An older specimen of Echinorhinus is proved to have a spine on a soft papilla; Scymnus has no spine; both have the general features of the Spinacidae. Two species of Cestracion are compared with C. philippi. Mustelus lunulatus lacks the pera and pseudosiphon of M. vulgaris. Dicerobatis has a peculiar scaphus, and the claspers end in a fimbriated manner. Pteroplatea resembles Trygon and Benthobatis and Astrape are both like Torpedo.The species are listed below.
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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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  • 99
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    Notes: In the blastula the region of accelerated cell division is on the ventral side of the egg, nearly opposite the site of the future beginning blastopore. The ventral wall of the blastocoele is thicker than the dorsal. In the very early gastrula a new region of accelerated cell division appears in the vicinity of the dorsal lip of the blastopore.A downward movement of material comprising the marginal zone of micromeres and the portion of the wall of the blastocoele immediately above it occurs during all the later blastula stages and continues until this material is carried below the level of the equator and involved in the process of gastrulation. On the dorsal side of the egg, this movement is more rapid than on the ventral side.In the late blastula stage there are evidences of growth in the region of smaller micromeres. In the very late blastula, a vertical groove appears at the dorsal margin of the floor of the blastocoele; this groove is believed to indicate the operation of factors concerned with gastrulation.In connection with the first nuclear division, evidences of cytoplasmic activity leading to the formation of the first cleavage furrow are described. As the blastomeres become smaller, progressive changes take place in the distribution of their cytoplasm.
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    Journal of Morphology 42 (1926), S. 335-348 
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A summary is given of the previous memoirs, and an attempt has been made, upon the three characters of this investigation, to arrange the genera into families, which agree, with two exceptions (Mitsukurina and Dicerobatis), with preexisting families. Some deductions are drawn as to relationships and attention is drawn to Cestracion galeatus and Triakis as connecting links. Separate families are erected for Dicerobatis and Mitsukurina, and the latter is placed near to Notidanus. Resemblances are shown between Chlamydoselachus and the Holocephali. The Trygonidae, Torpedinidae, and Rhinobatidae are singularly uniform families. An index is added both general and specific.
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