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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 50 (1930), S. 393-411 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the family Cottidae there is a greater variation in the shape of the sperm than has been found, with one exception, among all the remainder of the teleosts. There is an oval and a slender type of sperm with intergrading forms. The oval and the slender types vary, so that there is a more or less complete gradation from a nearly round, disc-shaped sperm to a slender, flattened sperm.Spermatid masses have been found only in some of the oval sperm forms. They have been found in seven species and subspecies of the genus Cottus and in three other genera of the family, but have not been found outside of the Cottidae. They occur in widely separated places, such as Norway and China, and in both fresh- and salt-water forms. In Cottus bairdii they are not found in all localities, their presence apparently being due to some external factor, perhaps temperature. It is highly probable that further investigation will show that in other species of the family, also, spermatid masses are present in some localities and not in others.
    Additional Material: 29 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    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.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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