448 BULLETIN OF THE 



concludes that the vesicle disappears after fecundation, whether as a 

 result of fecundation is uncertain (p. 204). Mayer seems also to have 

 seen in isolated cases of freshly laid eggs a " sort of Richtungsblaschen 

 in process of elimination " ; but he considers this process as also abnor- 

 mal, so that his subsequent suggestion, — that it were, perhaps, not too 

 venturesome to connect this with the eccentric position of the germina- 

 tive vesicle, — has not that importance in his mind which can fairly be 

 attributed to it to-day. 



Stossich (77) has extended his observations to the Echinoderms, 

 and maintains the same view relative to the morphology of the egg 

 which he previously expressed ('76). The germinative vesicle of the' 

 egg mature and ready for fertilization has a perfectly spherical form, 

 but no membrane ; its protoplasm is clear, transparent, homogeneous, 

 and slightly granular. He does not know that Hertwig's observations 

 of a delicate network within the germinative vesicle have been con- 

 firmed. If it had so complicated a structure, it could no longer be 

 regarded as a cell, but as a much more differentiated organism. The 

 germinative dot always has an eccentric position, is round, and contains 

 a very well pronounced nucleolinus. The author says he has several 

 times had the opportunity of seeing two germinative dots in a single 

 Q^^g. They were, however, always joined ; in these cases the nucleolini 

 were wanting. 



I do not doubt that these two "germinative dots" are really the 

 conjugating pronuclei, although the accompanying figure {hoc. cit, Tav. 

 I. Fig. 2) gives no evidence of the existence of polar globules or the 

 elevation of the membrane of the egg at any part of the periphery 

 which is shown. 



After fecundation the nucleolinus is no longer visible, and the con- 

 tours of the dot become always less decided, until they disappear with- 

 out leaving a trace. The vesicle from being round assumes an irregular 

 dentate outline. This change of form is only the effect of a movement 

 developed within the egg hy reason of contact with the sperm. 



Stossich desires his previous hypothesis, that the germinative vesicle 

 approaches the surface in consequence of the greater density of the 

 external layer of the yolk, to be so far corrected as to grant that this is 

 aided by the amoeboid motion of the vesicle. He is unable to say 

 whether the whole of the vesicle escapes as the two or three directive 

 vesicles. After the elimination of the last polar globule the yolk be- 

 comes homogeneous, then there is in its centre, after a little time, 

 a round body which becomes more distinct. It is the nucleus of the 



