OF THE VERTEBRATE OVARY. 591 



are again very different from those of Foulis. He finds certain 

 cords of cells in the hilus of the ovary, which he believes to be 

 derived from the Wolffian body, and has satisfied himself that 

 they are continuous with Pfliiger's egg-tubes, and that they 

 supply the follicular epithelium. To the general accuracy of 

 Kolliker's statements with reference to the relations of these 

 cords in the hilus of the ovary I can fully testify, but am of 

 opinion that he is entirely mistaken as to their giving rise to the 

 follicular epithelium, or having anything to do with the ova. 

 I hope to be able to give a fuller account of their origin than he 

 or other observers have done. 



My investigations on the mammalian ovary have been made 

 almost entirely on the rabbit the type of which it is most 

 easy to procure a continuous series of successive stages ; but 

 in a general way my conclusions have been controlled and 

 confirmed by observations on the cat, the dog, and the sheep. 

 My 'observations commence with an embryo of eighteen days. 

 A transverse section, slightly magnified, through the ovary at 

 this stage, is represented on PL 26, fig. 35, and a more highly 

 magnified portion of the same in fig. 35 A. The ovary is a cylin- 

 drical ridge on the inner side of the Wolffian body, composed 

 of a superficial epithelium, the germinal epithelium (g.e.}, and 

 of a tissue internal to this, which forms the main mass of 

 it. In the latter two constituents have to be distinguished 

 (i) an epithelial-like tissue (t), coloured brown, which forms 

 the most important element, and (2) vascular and stroma ele- 

 ments in this. 



The germinal epithelium is a layer about 0^03 0^04 mm. in 

 thickness. It is (vide fig. 35 A, g.e.) composed of two or three 

 layers of cells, with granular nuclei, of which the outermost 

 layer is more columnar than the remainder, and has elongated 

 rather than rounded nuclei. Its cells, though they vary slightly 

 in size, are all provided with a fair amount of protoplasm, and 

 cannot be divided (as in the case of the germinal epithelium of 

 Birds, Elasmobranchii, &c.), into primitive ova, and normal 

 epithelial cells. Very occasionally, however, a specially large 

 cell, which, perhaps, deserves the appellation primitive ovum, 

 may be seen. From the subjacent tissue the germinal epithe- 

 lium is in most parts separated by a membrane-like structure 



