STRUCTURE AND nEVELOPMENT OF VERTEBRATE OVARY. 391 



amongst epithelial cells continuous with the pseudo-epithelium, 

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

 sary to insist that this fact does not atford any argument in 

 favour of his interpretations. The ovarian region is honeycombed 

 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 extremities {;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 to indicate that they do not 

 essentially differ from cells which have the character of un- 

 doubted connective tissue cells, and renders it possible that the 

 greater part of the tunic, which has apparently the structure of 

 ordinary connective tissue, is in reality derived from the original 

 germinal epithelium, a view which tallies with the fact that in 

 some instances the cells of the tunic appear as if about to assist 

 in forming the follicular epithelium of some of the developing 

 ova. In Raja, the similarity of the pseudo-epithelium to the 

 subjacent tissue is very much more marked than in Scyllium. The 

 pseudo-epithelium appears merely as the superficial layer of the 

 ovarian tunic somewhat modified by its position on the surface. 

 It is formed of columnar cells with vertically arranged fibres 

 which pass into the subjacent layers, and chietiy differ from the 

 ordinary fibres in that they still form parts of the cell-proto- 

 plasm enclosing the nucleus. In PI. XIX, fig. 34, an attempt 

 is made to represent the relations of the pseudo-epithelium to 

 the subjjiceut tissue in Raja. Ludwig's figures of the pseudo-epi- 

 thelium of the ovary, in the regular form of its constituent cells, 

 and its sharp separation by a basement membrane from the tissue 

 below, are quite unlike anything which I have met with in my 

 sections either of Raja or Scyllium. 



Close to the dorsal border of the ovary the epithelial cells of 

 the non-ovarian region have very conspicuous tails, extending 

 into a more or less homogeneous substance below, which con- 

 stitutes a peculiar form of tunic for this part of the ovarian 

 ridge. 



In the full-grown female the stroma of the ovarian region is 

 denser and has a more fibrous aspect than in the younger 

 animal. Below the pseudo-epithelium it is arranged in two or 



