THE GENESIS OF THE EGG IN TRITON. 275 



vitellus lies in close contact with the germinal vesicle, 



except at one side, where a small space, probably caused 



by contraction, is seen. 



That the germinal vesicle in fig. 22 filled the whole cavity 



in the living ovum is very improbable, since it is not at 



all abnormally small — in fact is about equal to the germinal 



vesicle in fig. 27. 



In fig. 22 the nucleoplasm is a little more coarsely granular 



than the egg-protoplasm, except the peripheral portion, 



which contains the nucleoli, and .which is less coarsely 



granular than the central portion. 



The germinal vesicle has everywhere except on the side 



of contact a sharp outline, but there does not appear to 



be a double-contoured membrane. 



On the side of contact is seen an elongated area of per- 

 fectly homogeneous, non-granular, deeply-stained substance, 

 which extends a little beyond the limits of the germinal 

 vesicle in both directions. In this substance are seen two 

 or three of the germinal dots, and the substance is con- 

 tinuous with the nucleoplasm, from which it differs only by 

 having no granules. On the side of contact there is cer- 

 tainly nothing that could be called a membrane. It seems 

 probable that this non-granular substance is a part of the 

 germinal vesicle, and that the germinal vesicle itself is upon 

 the eve of certain internal changes, some of which are seen 

 in fig. 28. This germinal vesicle (fig. 28), belonging to an 

 ovum measuring "82 mm. in diameter, is still more flattened 

 than in fig. 22, and the outline is less regular, and shows 

 no sign of a membranous envelope. The germinal dots have 

 taken on peculiar forms, and appear to be moving towards 

 the centre of the vesicle. Several elongated forms are seen, 

 some of which are constricted about the middle, evidently in 

 process of division. In some cases the division is just on 

 the point of completion, the two halves still being joined by 

 only a slender thread. 



Another peculiarity, not observed in earlier stages, is the 

 vacuole-like space seen in most of the germinal spots. In 

 the elongated forms generally two such vacuoles, located at 

 the two poles, are seen, and sometimes the same number is 

 seen in the non-elongated massive forms. Hertwig (16) 

 has described similar appearances in the egg of Hsemopis 

 and in that of the Frog, and v. la Valette St. George (IT, 

 p. 58) has observed the same in the egg of one of the 

 Libellula. 



Together with this breaking up and centripetal movement 

 of the dots there is also a concentration of the coarser 



