Bennet Mills Allen 117 



Up to the stage of 8 clays after birth, there were found numerous 

 transition forms connecting the germinative cells with the primitive 

 sex cells. This is by no meins true of the 2-i-day stage (Plate YI, 

 Fig. 24), where there is a very sharp distinction between the two types 

 of cells which are singularly uniform among themselves. This is true 

 not only in the characters already enumerated, but also in the staining 

 reaction as Avell. The germinative nuclei take the iron hematoxylin 

 stain with avidity while the primitive sex cells (spermatogonia) are not 

 affected b}^ it at all. 



25 Days after Birth. Ovary. — The cords of Pfiilger are now almost 

 entirely broken up to form large numbers of small follicles surrounded 

 by connective tissue that has permeated the entire mass of each cord of 

 Pfiilger. 



31 Days after Birth. Ovary. — It was noted in an earlier stage (17- 

 day ovary) that certain ova of the innermost follicles degenerated 

 leaving clumps of follicular cells. These clumps are quite evident in the 

 31-day stage, lying along the border between the medulla and cortex. 



Jf5 Days after Birth. Ovary. — Many of the follicles have increased 

 in size until they have acquired as many as three layers of granulosa 

 cells, among which appears an incipient follicular cavity. Already 

 the stroma forms a capsular investment (theca) about each follicle, 

 and this investment has begun to show a ditferentiation into a theca 

 interna and a theca externa. The nuclei of the cells of the theca 

 interna are roimded and the cell body has become fuller in contrast 

 to the attenuated fibrous character of the cells of the theca externa, 

 whose nuclei have remained elongated and in every regard like those 

 of the general stroma tissue of which they are an integral part. Tran- 

 sition forms l^etween both varieties of theca cells can be readily found. 

 It might be Avell to call attention to the fact that there is a thin layer 

 of attenuated stroma cells between the theca interna and the mem- 

 brana propria of the granulosa layer. It will be termed the follicular 

 capsule. 



At this period many cells of the theca interna have developed into 

 interstitial cells similar to those described in the testis of the pig 

 embryo. Each has a rounded nucleus, clear cell outlines, centro- 

 sphere. centrosome and numerous fatty granules deposited in its 

 cytoplasm. The formation of these interstitial cells is genetically 

 connected with a process of follicle degeneration which continues from 

 the time of the earliest formation of follicles on through adult life. 



60 Days after Birth. Ovary. — The medulla becomes still more re- 

 duced in this sta2:e bv the invasion and growth of follicles in its bor- 



