276 T. IWAKAWA. 



nucleoplasmic elements, leaving a witler peripheral portion 

 than is seen in fig. 22, containing the less granular part of 

 the vesicle. 



In fig. 29 these changes are carried still further. The 

 germinal dots have been reduced by division to coarse 

 granules of various sizes, and have collected in a central 

 mass, leaving a broad peripheral portion almost as homo- 

 geneous as the small elongated mass at one side of the 

 vesicle in fig. 22. 



Scattered dots are seen in this peripheral portion. The 

 germinal dots appear to have undergone some change in 

 composition, judging from the effect of the staining fluid. 



In fig. 28 the nuclear substance is stained, but much less 

 strongly than the dots. In fig. 29 the nuclear substance is 

 coloured as before, but the fragments of the dots have a dull 

 yellowish-brown colour instead of the deep red of fig. 28. 



In fig. 29 the vitellus is in immediate contact with the 

 germinal vesicle, the clear space seen in fig. 22, which was 

 also present in fig. 28, having entirely disappeared. 



Owing to the limited amount of time which I have had 

 to devote to this part of my study, I have not been able to 

 learn the further course of events in the germinal vesicle. 



The " Yolk-nucleus." 



In small ova, measuring from '15 mm. to '16 mm., I have 

 several times met with an oval body at one side of the 

 germinal vesicle (fig. 8). I do not find this body in all 

 eggs of this size ; indeed, it may be said to be a rather rare 

 occurrence. This is undoubtedly the Dotterkern (not to be 

 confounded with the " Dotterkern " of Goette) of German 

 authors. 



Hertwig (16, p. 37) has proposed to designate this body 

 as " Dotterconcreme7it," in order to avoid the comparison 

 implied in the term " yolk-nucleus." I can say nothing in 

 regard to the origin or fate of this body, but as it is not 

 constant, no special importance can be attributed to it. It 

 has a granular composition, but this fact does not warrant 

 the opinion that it is a mere aggregation of yolk-granules. 



Van Bambeke refers the origin of this body to the folli- 

 cular epithelium, one of the cells of which gets loosened and 

 embedded in the ovum. 



Waldeyer (4, p. 75) remarks that this body is found only 

 in young ova ; later it appears to disappear completely. 



Leuckart (18) and others have made similar observations. 



