OVARY AND OVA IN LTJCIFUGA AND STYGICOLA. 229 



the latter which reaches down to the follicle and possibly affords later a means of 

 entrance of the spermatozoa to the mature egg. 



The Ova. In the smaller ova (under 400 /tin diameter), the nucleus is usually 

 quite distinct and has approximately one-third the diameter of the whole ovum. 

 The cytoplasm, not yet deeply laden with deutoplasm, has usually a reticulated or 

 alveolar appearance. In the larger ova (over 400 /A in diameter), the cytoplasm 

 becomes more and more heavily laden with deutoplasm, until in the largest it is 

 almost wholly obscured by the latter. The nucleus at the same time becomes cor- 

 respondingly more difficult to find, not increasing much in size as the ovum develops. 

 No traces of maturation were detected in even the largest ova found (750 /A and over 

 in diameter). 



More or less deeply within the stroma the ova arise in masses of several hundred 

 ova each. In size the smallest discernible ova measure from 5 to 10 ^ in diameter 

 and have well-defined nuclei (s.o., plate 28, fig. A). As development proceeds a 

 number of ova in each "nest" may increase more than the others; at a later stage 

 it can be seen that a few of these are gaining on their fellows ; and still later one is 

 seen to be outstripping all the others in that "nest." Sometimes one (l.o., plate 28, 

 fig. A) gains the ascendency so early that the remainder (s. o., plate 28, fig. A) never 

 show any marked increase or difference in size among themselves. In any case, 

 in the final stage of development, a single ovum is left in the "nest," and this now 

 seems to migrate till it rests just beneath the surface of the ovary itself (o., plate 28, 

 fig. c). Where several large ova seem to have been developed in one "nest," close 

 scrutiny, at least in the case of the less fully developed ova, invariably reveals a 

 separating layer of very thin, elongated stromal cells (st.c., plate 28, fig. F) such as 

 originally surrounded the whole "nest" (compare with st.c., plate 28, figs. A or 

 D), thus showing that these larger, closely adjacent ova are derivatives each 

 from an originally distinct "nest." 



The fate of the other ova which at first lay in the same "nest" with the larger 

 ovum is a question of interest. Two possibilities suggest themselves: either the 

 growing ovum absorbs the neighboring ova into its own substance, or they disinte- 

 grate in situ without becoming a part of the larger ovum. 



Certain of the larger ova very strongly suggest the first possibility. In these 

 the smaller ova are grouped together at the side of the much larger one, or may even 

 surround it, and are apparently undergoing a greater or less amount of disintegra- 

 tion. In the case shown (a. o., plate 28, fig. B) this disintegration has gone so far that 

 the outlines of the small ova are quite indistinct and in some cases apparently only 

 the nucleus remains, and this, too, is no more than an irregular mass of chromatin. 



The atrophy of the small ova is evidently a rapid one, for there is no sign of any 

 pigmentation or other mark of a gradual degeneration of the cells. Moreover, wher- 

 ever a "nest" contains a larger ovum and smaller atrophying ova around it, the 

 cytoplasm of the ova is confluent, at least in the case of those most advanced in dis- 

 integration. This in itself is good evidence of the assimilation of the degenerating 

 ova by the larger one. In short, there is here a struggle for existence among the ova 

 of each ' ' nest. ' ' The successful ovum either produces a rapid degeneration of the sur- 

 rounding ova, or taking advantage of such a condition produced in them by some 

 unknown factor, assimilates them into its own substance. It is hard to deter- 

 mine what is the all-important cause of the initiation of the more rapid growth of 



