The development of the frog's egg : an introduction to experimental embryology / by Thomas Hunt Morgan.

  • Morgan, Thomas Hunt, 1866-1945.
Date:
1897
Catalogue details

Licence: Public Domain Mark

Credit: The development of the frog's egg : an introduction to experimental embryology / by Thomas Hunt Morgan. Source: Wellcome Collection.

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    Rath, and we must suspend judgment until further work throws more light upon the question. The spermatogenesis of the frog has not been worked out in the same detail as that of the salamander, yet vom Rath (’95) has made certain important statements in regard to it. Tlie prophase of the mitoses, before the ripening period, has in the frog a close resemblance to the skein-stage of the heterotypic and homoeotypic variations in the salamander. But, on the other hand, in the metakinetic stage the peculiarities of the homoeotypic and heterotypic forms, as described by Flemming, Fig. 6. — Stages in the last maturation-division of sperm-cells of Frog. (After vom Rath.) (Figs. C, D, F slightly modified.) are absent. The formation of the chromatin-rings and tetrad- groups in the frog (Fig. 6, A, B, C) differs from that of the sala- mander and is much more like that of Giyllotalpa. The rings, owing to the strong contraction of the segments, are relatively small in the frog, but proportionately thick (Fig. 6. B). From each ring arise the four spherical chromosomes of each tetrad- group (Fig. 6, C). The ring-stage lasts quite long in Rana, judging from the frequency of its presence. The rings lie at the periphery of the nucleus.