STRUCTURE AND DEVELOPMENT OF VERTEBRATE OVARY. 329 



Plluger. These columns are formed of normal cells of the ger- 

 minal epithelium, wjiich enclose ovarian nests and ova in all 

 stages of development. A comparison of the section I have 

 represented, with those from previous stages, appears to me to 

 demonstrate that the relation of the epithelium and stroma has 

 been caused by an ingrowth or penetration of the stroma into 

 the epithelium, and not by a mutual intergrowth of the two tissues. 

 Although the ovary, of which fig. 26 represents a section was 

 from Sc^. stellare, and the previous ovaries have been from «S'ty. 

 cani-ida, yet the thickness of the epithelium may still be ap- 

 pealed to in confirmation of this view. In the previous stage the 

 thickness was about 0*096 mm., in the present one it is about 

 O"] (j mm., a difference of thickness which can be easily accounted 

 for by the growth of the individual ova and the additional tracts 

 of stroma. A pseudo-epithelium is more or less charly formed, 

 but it is continuous with the columns of epithehuin. In the 

 stroma many isolated cells are present, which appear to me, from 

 a careful comparison of a series of sections, to belong to the 

 germinal epithelium. 



The thickness of the follicular epithelium on the inner side 

 of the larger ova deserves to be noted. Its meaning is discussed 

 on page 399. 



Quite a different interpretation to that which I have given 

 has been put by Ludwig and Semper upon the parts of the 

 ovary at this stage. My psendo-epithelmm is regarded by 

 them as forming, together with the follicular epithelium of the 

 ova, the sole remnant of the original germinal epithehum ; and 

 the masses of cells below the pseudo-epithelium, which I have 

 attempted to show are derived from the original germinal epi- 

 thelium, are regarded as parts of the ingrowths of the adjacent 

 stroma. 



Ludwig has assumed this interpretation without having had an 

 opportunity of working out the development of the parts, but 

 Semper attempts to bring forward embryological proofs in support 

 of this position. 



If the series of ovaries which I have represented be examined, 

 it will not, I think, be denied that the general appearances are 

 very much in favour of my view. The thickened patch of ovarian 

 epithelium can apparently be traced through the whole series of 

 sections, and no indications of its sudden reduction to the thin 

 pseudo-epithelium are apparent. The most careful examination 

 that I have been able to make brings to light nothing tending to 

 show that the general appearances are delusive. The important 

 difference between us refers to our views of the nature of the 

 tissue sutyacent to the pseudo-epithelium. If ray results be ac- 

 cepted, it is clear that the whole ovarian region is an epithelium 



