OF THE VERTEBRATE OVARY. 557 



increase and arrange themselves around the ova as follicle 

 cells." 



Although the histological changes which take place in the 

 succeeding stages are not inconsiderable, they do not involve 

 any fundamental change in the constitution of the ovarian 

 region, and may be described with greater brevity than has been 

 so far possible. 



In a half-grown female, with an ovarian region of 3 mm. in 

 breadth, and O'8 mm. in thickness, the stroma of the ovarian 

 region has assumed a far more formed aspect than before. It 

 consists (PI. 24, fig. 10) of a basis in most parts fibrous, but in 

 some nearly homogeneous, with a fair number of scattered cells. 

 Immediately below the pseudo-epithelium, there is an im- 

 perfectly developed fibrous layer, forming a kind of tunic, in 

 which are imbedded the relatively reduced epithelial trabeculae 

 of the previous stages. They appear in sections as columns, 

 either continuous with or independent of the pseudo-epithelium, 

 formed of normal cells of the germinal epithelium, nests of ova, 

 and permanent ova in various stages of development. Below 

 this there comes a layer of larger ova which are very closely 

 packed. A not inconsiderable number of the larger ova have, 

 however, a superficial situation, and lie in immediate contact 

 with the pseudo-epithelium. Some of the younger ova, enclosed 

 amongst epithelial cells continuous with the pseudo-epithelium, 

 are very similar to those figured by Ludwig. It is scarcely 

 necessary to insist that this fact does not afford any argument 

 in favour of his interpretations. Tire ovarian region is honey- 

 combed by large vascular channels with distinct walls, and 

 other channels which are perhaps lymphatic. 



The surface of the ovarian region is somewhat irregular and 

 especially marked by deep oblique transverse furrows. It is 

 covered by a distinct, though still irregular pseudo-epithelium, 

 which is fairly columnar in the furrows but flattened along the 

 ridges. The cells of the pseudo-epithelium have one peculiarity 

 very unlike that of ordinary epithelial cells. Their inner ex- 

 tremities (vide fig. 10) are prolonged into fibrous processes 

 which enter the subjacent tissue, and bending nearly parallel 

 to the surface of the ovary, assist in forming the tunic spoken 

 of above. This peculiarity of the pseudo-epithelial cells seems 



