124 BERTRAM G. SMITH 



stain like chromatin (see fig. 25), These are evidently formed in 

 close association with the chromosomes; in earlier stages chromo- 

 somes have been found covered with these granules before the 

 latter have appeared elsewhere. 



In the ovarian eggs of an adult killed August 22, the most 

 marked changes in the general topography as viewed in meridional 

 sections are a slight advance in the migration of the germinal vesi- 

 icle toward the surface, and an increased thickness of the periph- 

 eral zone of fine yolk particles, particularly in the yolk disc. 

 In the vegetal hemisphere the protoplasmic mantle is no longer 

 recognizable as a separate layer; its constituents have mingled 

 with the peripheral layer of fine yolk particles. The cytodisc 

 is reduced in thickness by the blending of its inner surface with 

 the yolk disc. 



The narrow path of cytoplasm leading toward the center of the 

 egg from the apex of the cone of cytoplasm underlying the germi- 

 nal vesicle has disappeared; likewise the yolk cup is, as a rule, no 

 longer present. In this stage there is a slight increase in the num- 

 ber of chromatin granules dispersed amongst the nucleoli; other- 

 wise the nuclear contents seem unchanged. 



Ovaries taken during the last week in August and the first week 

 in September usually contain some eggs with the germinal vesicle 

 appearing at the surface. In the general organization of the egg 

 before the germinal vesicle actually reaches the surface, there are 

 few changes from the condition described for August 22. Fig. 

 26 shows the general topography of an egg with the germinal vesi- 

 cle very close to the surface. The cone of cytoplasm underlying 

 the germinal vesicle is beginning to mingle with the yolk; it is not 

 present in the section figured. Within the germinal vesicle the 

 nucleoli are massed more closely together at the center; there is an 

 increase in the number of chromatin granules, and apparently a 

 gradual disappearance of the chromosomes — in some eggs they 

 could not be found. 



At the close of the period considered, axial differentiation is 

 evident in the following arrangement of material: (a) the excen- 

 tric position of the germinal vesicle and the cone-shaped mass 

 of cytoplasm underlying it; and (b) the formation about the animal 



