1880.] in the common Foicl and in the Rahbit. 245 



to the periphery of the ovum by branching processes. The rest of the 

 contents of the ovum is clear. 



Tost- Embryonic Formation of Graafian Follicles in the Bitch. 



In sections of the ovary of a bitch-pup of eighteen days it is easy to 

 convince oneself of the glandular mode of formation of the Graafian 

 follicles and their contents. Figs. 30 to 33 are representations of 

 such ovarial glands, showing their communication at this period with 

 the surface of the ovary. In fig. 30 this communication is direct, 

 and the whole structure bears a striking resemblance to a racemose 

 gland whose saccules are filled with cells ; in fig. 31 the glands are 

 longer and more irregular, and the duct, if we may call it so, does not 

 pass straight to the surface, but in an oblique or even convoluted 

 manner. It is impossible to confound glandular tubes of this descrip- 

 tion with creases upon the surface of the ovary, as Foulis suggests 

 that Pfliiger and Waldeyer have done ( 18 ), especially since in many 

 cases where the tubes are cut across, the lumen can be distinctly seen 

 (Fig. 32). 



We can see in the figures how portions of these solid columns of 

 cells are becoming cut off into " egg-nests " by ingrowths of the ovarial 

 matrix. In many of these nests the primitive ova are already distin- 

 guishable from the other cells by their size and the clearness of their 

 protoplasm. But it often happens that the distinction does not appear 

 until the group of cells which constitutes the nest is completely 

 separated from the rest of the egg-tube. Fig. 24 from the rabbit's 

 ovary illustrates the same fact. 



In sections of the ovary of a young but nearly full-grown bitch the 

 same glandular character of the superficial parts of the egg-tubes of 

 Pfliiger is evident (fig. 34). ( 19 ) In most the open communication 

 with the surface is lost, and the solid ends of the glands, which form 

 the " egg- columns," properly so-called, have also become severed, and 

 have sunk into the ovarial stroma. But the lumen of the tube is still 

 distinct, and the section is wonderfully like that of the duct of a small 

 secreting gland. 



Appearances like these seem to me to point very clearly to the 

 conclusion that the typical mode of formation of the Graafian follicles 

 and their contents is by a gland-like ingrowth of the ovarial epi- 

 thelium, and that the process, which is described by Balfour, as 

 occurring in the Elasmobranch and in the rabbit, is a modification 

 of this typical mode. For it must certainly be admitted that the 

 deeper-seatedness of the columns of germinal epithelium as the ovary 

 advances in development, cannot be wholly due to the outward growth 

 of the ovarian stroma, since we see how that even after the ovary has 

 attained its full size the Graafian follicles (which are derived from 



vol. xxx. s 



