No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 471 
ovum commencing to outstrip the others in point of size, i.e. t 
in rapidity of growth, until we reach a point where this fortu¬ 
nate cell nearly fills the whole cavity of the acinus, driving the 
neighboring 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 sufficient 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 v 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 urns 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 
