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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 49 (1930), S. 415-453 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The male and female germ cells of Polygra appressa were found occurring together in the acini from the time the snails were 5 mm. in width onward, and their development traced backward to the gonial stage, in which the aspect of the female cells, present in small numbers in the acinus wall, and the male cells, in greater numbers in the lumen, seems identical.In oocytes, differentiation involves the enormous increase in volume of cell, nucleus, and plasmosome; the appearance of yolk and of a secondary nucleolus attached to the first one, and, in some cells, various other nucleoli, attached to the chromosomes. Meanwhile the chromosomes become diffuse and spread into the interior of the nucleus, finally condensing again on the periphery. The employment of various technical methods produced interesting variations in the aspect of oocyte chromatin and nucleoli.The appearance of the Nebenkern in spermatocytes during the growth period was noted, but no indication of its presence discovered in oocytes until the fairly late growth period.The chromosome forms were noted in spermatogonia, first spermatocytes and oocytes, and their numbers found to be 61 63, 31, and 31, respectively, but no clear dividing oogonia were found, on which similar observations could be made.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 63 (1938), S. 421-439 
    ISSN: 0362-2525
    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.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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