182 BULLETIN OF THE 



I have noticed that very often the constriction about the base of the 

 second polar cylinder advanced much more rapidly from one side than 

 from the other, so that the axis of the cylinder, or becoming globule, 

 regularly assumed a direction quite oblique to that of the polar axis of 

 the yolk, and that (Fig. 19) consequently the point of final attachment 

 was uniformly at some distance from the animal pole. 



The second globule is very often somewhat smaller than the first, hav- 

 ing three quarters or only two thirds the diameter of the latter. When 

 first detached the second seems to push before it the first, but at length 

 they assume positions alongside each other in contact with the vitellus. 



I have never observed i\iQ formation of more than two polar globules, 

 and never, when traced under normal conditions, a less number. Neither 

 have I seen anything which could be compared to a division of either of 

 the already formed polar globules, nor yet, with the exception of a sin- 

 gle somewhat doubtful case, any instance in which as many as three 

 globules existed near a single vitellus. 



I have noticed no' other constant differences in the polar globules. 

 The interval between them and the vitellus increases after the detach- 

 ment of the second globule, but subsequently both come to lie much 

 closer to the yolk, almost always in immediate contact with it. Both 

 often retain a spherical form for a considerable time, during several 

 successive segmentations at least. In other cases, one or both exhibit 

 an irregular and wrinkled appearance, due most likely, in all cases, to 

 such a collapse and partial loss of substance as have in several instances 

 been directly observed. I believe that there is no regularity about 

 this, and that one globule is quite as likely to present this appearance 

 as the other, if only one is thus affected. In this collapsed condition 

 they continue to exist even in the most advanced stages. As is well 

 known, they take no part in the formation of the tissues of the em- 

 bryo. 



We will now return to a consideration of the vitellus. Much as in 

 the case of the first polar globule, the changes in the form of the 

 yolk which accompany the production of the second are followed by 

 an externally quiescent state, in which the vitellus, having once more 

 assumed the spherical form, seems to be resting from its labors. The 

 crescent-like shell of clear protoplasm at the animal pole again suf- 

 fers the vitelline granules to encroach upon its acquired territory, so 

 that the observer sees only a very neatly outlined sphere. It appears 

 whitish, or slightly yellowish, in reflected light, and more or less opaque 

 when viewed with transmitted light ; it hangs suspended in the albu- 



