No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 471 



ovum commencing to outstrip the others in point of size, i.e., 

 in rapidity of growth, until we reach a point where this fortu- 

 nate cell nearly fills the whole cavity of the acinus, driving the 

 neishboring: ova aside. Those cells which come into contact 

 with such a rapidly growing ovum, as well as those in more 

 proximal portions of the acinus which did not chance to lie 

 close to the wall of the acinus, do not develop further, but 

 disintegrate, and various stages of such disintegration may be 

 seen in the cavity of the acinus, such as irregular cells with a 

 nucleus, those which have lost their nuclei, and finally refrac- 

 tive cytoplasmic masses which stain deeply with eosin (the 

 cytoplasm of the developing ova stains with haematoxylin). 

 Perhaps such degenerated masses of cellular substance are des- 

 tined to be assimilated by their more fortunate brethren. Often 

 a number of such degenerating ova are to be seen grouped at 

 one pole of a large ovum, and these cases present a certain 

 similarity to cleavage stages, the large ovum resembling a 

 macromere, the others micromeres. It is not difficult to find 

 an explanation for the disintegration of certain of the ova, for 

 only those close to the wall of the acinus can procure nourish- 

 ment in amount sufificient for their growth, since this nour- 

 ishment must be derived through the wall of the acinus from 

 the body cavity (there being no yolk in the ova) ; and the 

 peripherally situated ova must obtain all the nourishment thus 

 furnished, so that those in the center of the acinus simply die 

 for want of food. Further, a particular ovum of those placed 

 peripherally, if it procures a greater amount of nourishment 

 than its neighbors do, because, e.g., of being in contact with a 

 greater surface of the wall of the acinus, grows faster than the 

 others and, pushing them aside, eventually gets full control of 

 the whole amount of nourishment, so that a slight advantage at 

 the start would increase in value in a geometrical ratio. Here, 

 accordingly, we have a beautiful example of that process termed 

 by Roux "der Kampf der Theile ums Dasein," that cell becoming 

 a mature ovum which has succeeded in obtaining the greatest 

 amount of nourishment. It is also interesting to note the 

 position of the nucleus within the growing ovum ; in all the 

 younger stages of the egg it is placed in that part of the cell 



