. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 146 S. \rALLWOOD. [VOL. II. The central corpuscle becomes the centrosome. Sections of the ovotestis before copulation show the unfertilized egg lying free in the follicles of the hermaphroditic gland. The large germinal vesicle lies in the center of the egg ; it contains a large vacuolated nucleolus, also basichromatin and oxychroma- tin granules. The deutoplasmic spheres are equally distributed in the cytoplasm and conceal its structure. I have not been able to discover any evidence of a central corpuscle or centrosome in t
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 146 S. \rALLWOOD. [VOL. II. The central corpuscle becomes the centrosome. Sections of the ovotestis before copulation show the unfertilized egg lying free in the follicles of the hermaphroditic gland. The large germinal vesicle lies in the center of the egg ; it contains a large vacuolated nucleolus, also basichromatin and oxychroma- tin granules. The deutoplasmic spheres are equally distributed in the cytoplasm and conceal its structure. I have not been able to discover any evidence of a central corpuscle or centrosome in the egg before mitosis begins. By the time the eggs are laid the first polar spindle is in the end of the prophase. In order to secure the earlier stages, a large number of animals were collected and killed as soon as they began to lay. The first polar spindle begins to form as the animals begin to lay. Sections 'of the ovotestis taken from animals killed while they were laying revealed the fact that every mature egg had already passed through the early prophase of the first spindle ; even those eggs in the most distant follicles, where it is prob- able that the sperms from the receptaculum seminalis had not penetrated ; I have found the sperms in the anterior part of the herma- phroditic duct, but not extending back to any considerable distance. The earliest stage thus far discovered had two well- FI<;. i. -Taken from the formed central corpuscles and a definite cen- tral sPittdle connecting each, which passed. rounded by the cortical through the germinal vesicle, the walls of zone of the sphere. The , . , 1-1 • 'i_1 T-t central spindle is weii which are plainly visible. The ring-shaped formed and the chromo- chromosomes have begun to form from the somes are forming into the first equatorial plate, meshwork of linin and chromatin. The re- Walls of the germinal -\ . • c . i i i i vesicle still present, auction of the chromosomes has not been sperm entering at vege- worked
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
