THE GENESIS OF THE EGG IX TRITON. 271 



there can be little doubt that some of the nuclei seen on and 

 around the ovum in fig. 17 correspond to the follicular nuclei 

 -seen in fig. 18. 



The nuclei around the ovum (fig. 19) are precisely like 

 those around the small germ-cells, and these nuclei are to 

 be found around the germ-cells which have multiple nuclei, 

 as well as around those with simple nuclei. While thus 

 my observations incline me to the theory of the epithelial 

 origin of the granulosa, I cannot regard them as conclusive. 

 The origin of the ovum, according to the above observa- 

 tions, may be briefly stated in the following words : 



A nucleus of a germinal epithelial cell divides into two ; 

 one remains as the nucleus of the proliferating cell, the 

 other enlarges and becomes the centre of a well-defined 

 portion of the protoplasm belonging to the parent-cell. The 

 germ-cell thus formed lies at first wholly within the parent- 

 cell, but as it increases in size it expands beyond the limits 

 of the latter, and sinks beneath the surface, becoming at the 

 same time free from the mother-cell. 



Epithelial cells crowd around the germ-cell, and some, 

 sinking beneath the surface with it, form a follicular (?) 

 wall around it. The germ-cell represents a primordial 

 ovum, or a cell from which the primordial ovum plus the 

 follicular epithelium arise. 



Formation of Yolk-spherules. 



In the young germ-cells the protoplasm is clear and trans- 

 parent, like that of the epithelial cells. The first plain in- 

 dication of the presence of yolk-spherules appears about the 

 time the egg has attained a diameter of '25 mm. At this 

 time the ovum appears as represented in fig. 20. 



The protoplasm has become somewhat clouded with very 

 minute granules ; and scattered patches, consisting of larger 

 or smaller aggregations of small yolk-spherules, are seen on 

 one side of the ovum lying near the periphery. These aggre- 

 gations are quite opaque, although the single spherules are 

 not so. Viewed singly, after being expelled by pressure of 

 a cover from a ruptured ovum, they appear to be minute 

 shining spherules, measuring about '001 mm. They have a 

 refrangibility much like that of particles of fat, and show 

 the usual Brownian movement. Along with aggregations 

 numbering from 20 — 25 spherules are found others consist- 

 ing of only two or three. The spherules of the patches do 

 not vary much in size ; but outside these patches are found 

 single spherules, varying from the size of those in the 



VOL. XXII. NEW SER. S 



