38S F. M. BALFOUR. 



fig. 9 a section through the whole ovarian ridge slightly magnified. 

 Its breadth is now 1-3 mm., and its thickness 0-3 mm. The 

 ova have grown very greatly, and it appears to me to be mainly 

 owing to their growth that the greater thickness of the epithelium 

 is due, as well as the irregularity of its inner suiface {vide tig. 9). 



The general relation of the epitiielium to the surrounding 

 parts is much the same as in the earlier stage, but two new 

 features have appeared — (1) The outermost cells of the ovarian 

 region have more or less clearly arranged themselves as a 

 kind of epithelial covering for the organ ; and (2) the stroma 

 ingrowths of the previous stage have become definitely vascular, 

 and have penetrated through all parts of the epithelium. 



The external layer of epithelium is by no means a very marked 

 structure, the character of its cells vary greatly in difi'erent 

 regions, and it is very imperfectly separated from the subjacent 

 layer, I shall speak of it for convenience as pseudo-epithelluin. 



The greater part of the germinal epithelium forms anasto- 

 mosing columns, separated by very thin tracts of stroma. The 

 columns are, in the majority of instances, continuous with the 

 pseudo-epithelium at the surface, and contain ova in all stages 

 of development. Many of the cells composing them naturally 

 form the follicular epithelium for the separate ova ; but the 

 majority have no such relation. They have in many instances 

 assumed an appearance somewhat different from that which they 

 presented in the last stage, mainly owing to the individual nuclei 

 being more widely separated. A careful examination with a 

 high power shows that this is owing to an increase in the amount 

 of protoplasm of the individual cells, and it may be noted 

 that a similar increase in the size of the bodies of the cells has 

 taken place in the pseudo-epithelium and in the follicular epithe- 

 lium of the individual ova. 



The stroma ingrowths form the most important feature of 

 the stage. In most instances they are very thin and delicate, 

 and might easily be overlooked, especially as many of the cells 

 in them are hardly to be distinguished, taken separately, from 

 those of the germinal epithelium. These features render the in- 

 vestigation of the exact relation of the stroma and e|nthelium 

 a matter of some difficulty. I have, however, been greatly 

 assisted by the investigation of the ovary of a young exani])le of 

 Scyllium Stella re, 16^ centimetres in length, a section of which 

 is represented in PI. XVllI, fig. 26. In this ovary, although no 

 other abnormalities were observable, the stroma ingrowths were 

 exceptionally wide; indeed, quite without a parallel in my series 

 of ovaries in this respect. Tlie stroma most clearly divides up the 

 epithelium of the ovary into separate masses, or more j)robabIy 

 anastomosing columns, the equivalents of the egg-tubes of 



