STRUCTURE OF THE OVUM. 



179 



principal yolk, refracting light strongly, and of large size in 

 proportion to the cell. These large highly refractile nuclei give 

 a very characteristic appearance, recognizable at first sight, to 



Fig. 193. 



Fig. 193. A, Primordial egg of Man, from a foetus at the eighth 

 month (Hartnack 2-9) ; B, primordial follicle from a Rabbit ; c, primor- 

 dial follicle from a Pigeon ; D, a somewhat older follicle from the 

 same animal, exhibiting the commencement of the formation of the 

 secondary yolk ; E, csecal extremity of the ovary of the Ascaris nigro- 

 venosa, exhibiting germinal vesicles (in part with germinal spot and 

 Schron's " granule ") in a diffused mass of protoplasm ; F, an egg of the 

 Ascaris nigro-venosa, from about the middle of the ovary, exhibiting 

 Schron's granule and the commencement of the deposit of a yolk ; 

 G, an egg from a follicle of a Rabbit, two millimeters in thickness ; 

 a, epithelium of the ovum ; 6, radially striated zona pellucida ; c, ger- 

 minal vesicle ; d, germinal spot ; e, yolk. (B G, Hartnack 3-9. ) 



cells of the ovum. Up to the present time I have never 

 more than one nucleus in each cell of the ovum. Kolliker, 



N 2 



