. Senescence and rejuvenescence. Age; Reproduction. THE GAMETES IN PLANTS AND ANIMALS 343 fertilization, and zygogenic eggs which require fertilization before development. It is a fact of great interest that in such cases the parthenogenic eggs usually differ morphologically from the zygo- genic eggs. In Sida crystallina, one of the cladoceran Crustacea, for example, the parthenogenic eggs are smaller and contain less yolk. Figs. 178-180.—Three stages in the differentiation of the egg, 0, of Hydra. From Downing, '09. than the zygogenic eggs. Fig. 192 shows an ovarian tubule of this species con
. Senescence and rejuvenescence. Age; Reproduction. THE GAMETES IN PLANTS AND ANIMALS 343 fertilization, and zygogenic eggs which require fertilization before development. It is a fact of great interest that in such cases the parthenogenic eggs usually differ morphologically from the zygo- genic eggs. In Sida crystallina, one of the cladoceran Crustacea, for example, the parthenogenic eggs are smaller and contain less yolk. Figs. 178-180.—Three stages in the differentiation of the egg, 0, of Hydra. From Downing, '09. than the zygogenic eggs. Fig. 192 shows an ovarian tubule of this species containing various stages of parthenogenic oogenesis. The primitive cells {pc), formed at the upper end of the tubule, after the period of division is over arrange themselves in groups of four (g> i) of which the third from the upper end develops into an. 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 Child, Charles Manning, 1869-1954. Chicago, Ill. , The University of Chicago Press
Size: 1433px × 1744px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectreproduction, bookyea
