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 s P ittdle 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 out in detail. These ring-shaped 



tal pole. 



chromosomes gradually take a deeper stain 

 and come to lie in the equatorial plate of the first polar 

 spindle (Fig. i). In a cross-section of the equatorial plate 

 I was able to count sixteen distinct chromosomes. There 

 is a distinct cortical zone surrounding the central corpuscle. 

 The astral rays pass through this clear area and extend 

 to the central corpuscle. At this stage I have been able to 



