OVARIES IN TELEOSTEAN AND ELASMOBEANCH FISHES. 205 



ness. Accordingly it presents a veiy different appearance 

 indeed from the single layer of columnar cells surrounding 

 the immature (fig. 19) and doubtless also the ripe ovum. It 

 would seem at first glance as if a great proliferation of the 

 follicular epithelial cells had taken place. I do not, however, 

 think that there has been any proliferation. There were 

 certainly no signs of karyokinesis in these cells. If we allow 

 for the enormous contraction of the follicle which must have 

 taken place, the thickness of the follicular epithelium becomes 

 intelligible. As a result of the contraction there is no longer 

 room for the follicular epithelial cells to remain spread out in 

 a single layer over the inside of the thee a, and accordingly 

 some of the cells have been squeezed out between the others, 

 so as to give the false appearance of a tissue several cells 

 thick. The irregular arrangement and shape of the cells, 

 especially towards the inside of the follicular epithelium, 

 bears out this view. 



The membrana propria folliculi in these preparations 

 has a puckered appearance, no doubt due, partly at least, 

 to contraction. At very numerous points in a cross-section 

 of such a recently ruptured follicle the membrana propria 

 is folded inwards, and strands of cells from the theca have 

 grown into these folds, so that we have already a hint of the 

 radial structure of the mammalian corpus luteum as described 

 and figured by Sobotta (1895). The venous blood-vessels in 

 the theca have not as yet commenced to grow in towards the 

 cavity of the follicle as occurs later (fig. 31), and there is no 

 trace of blood or blood corpuscles in the cavity of the follicle, 

 only a kind of plasma, probably derived from the secretion 

 of the follicular epithelial cells. 



Sections were also made of an ovary of Spin ax in which 

 corpora lutea in a more advanced stage of development 

 were present. The ovary in question was that of a female 

 towards the end of gestation. The young were almost readj^ 

 for birth. Since this specimen was caught in the same month 

 as the other one in which the ova had just descended into the 

 oviduct, and in whose ovary the recently ruptured follicles 



