. The biology of the amphibia. Amphibians. Fig. 8.—Stages in the spermatogenesis of Rana temporaria. A. Metaphase of a spermatogonial division showing the 26 chromosomes characteristic of this species. B. Second maturation division showing the x and y chromosomes (in outline) between the autosomes. C. Immature spermatozoon. (After Witschi.) moment of fertilization has only half the chromosome number found in the body cells (Fig. 8). The union with the male nucleus (which by a similar pair of divisions has reduced its chromosome number by half) results in the restoration of the original somatic
. The biology of the amphibia. Amphibians. Fig. 8.—Stages in the spermatogenesis of Rana temporaria. A. Metaphase of a spermatogonial division showing the 26 chromosomes characteristic of this species. B. Second maturation division showing the x and y chromosomes (in outline) between the autosomes. C. Immature spermatozoon. (After Witschi.) moment of fertilization has only half the chromosome number found in the body cells (Fig. 8). The union with the male nucleus (which by a similar pair of divisions has reduced its chromosome number by half) results in the restoration of the original somatic number of chromosomes. This number is constant for the species, ranging from 32 for Alytes to 12 for Pelodytes. Several frogs and salamanders have a somatic number of 24. In Rana pipiens, R. palustris, and R. sylvatica there are 26 chromosomes; in several species of Bufo only 22 (Stohler, 1928). The spermatozoon brings to the egg little besides this nuclear matter. The acrosome or point (Fig. 6) is formed by the trans- formation of certain cytoplasmic materials, the product of the Golgi bodies, and may possibly represent a secretory granule. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Noble, Gladwyn Kingsley, 1894-1940. New York : McGraw-Hill
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Keywords: ., bookcentury1900, bookpublishernewyorkmcgr, booksubjectamphibians
