120 F, M. BALFOUR. 



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 

 (fluid coagulum) ; but this is sometimes absent, and it is then 

 very difficult to determine with exactness the inner border of 

 the epitbelium. The tissue {i), which forms the greater mass 

 of the ovary at this stage, is formed of solid columns or trabe- 

 culfe of epithelial-like cells, which present a very striking re- 

 semblance in size and character to the cells of the germinal 

 epithelium. The protoplasm of these cells stains slightly more 

 deeply with osmic acid than does that of the cells of the germinal 

 epithelium, yo that it is rather easier to note a difference be- 

 tween the two tissues in osmic acid than in picric acid specimens. 

 This tissue approaches very closely, and is in many parts in actual 

 contact with the germinal epithelium. Between the columns of 

 it are numerous vascular channels (shown diagrammatically 

 in my jBgures) and a few normal stroma cells. This remark- 

 able tissue continues visible tbrough the whole course of the 

 development of the ovary, till comparatively late in life, and 

 during all the earlier stages might easily be supposed to be 

 about to play some part in the development of the ova, or 

 even to be part of the germinal epithelium. It really, how- 

 ever, has nothing to do with the development of the ova, 

 as is easily demonstrated when the true ova begin to be 

 formed. In the later stages, as will be mentioned in the descrip- 

 tion of those stages, it is separated from the germinal epi- 

 thelium by a layer of stroma ; though at the two sides of 

 the ovary it is, even in later stages, sometimes in contact with 

 the germinal epithelium. 



In most parts this tissue is definitely confined within the 

 limits of the ovary, and does not extend into the mesentery 

 by which the ovary is attached. It may, however, be traced at 

 tJie anterior end of the ovary into connection with the walls of 

 the Malpighian bodies, which lie on the inner side of the Wolffian 

 body {vide fig. 35b), and I have no doubt that it grows out 

 i from the walls of these bodies into the ovary. In the male it 

 appears to me to assist in forming, together with cells derived 

 from the germinal epithelium, the seminiferous tubules, the 

 development of which is already fairly advanced by this stage. 

 I shall speak of it in the sequel as tubuliferous tissue. The 

 points of interest in connection with it concern the male 

 sex, which I hope to deal with in a future ])aper, but I have 

 no hesitation in identifying it with the segmental cords {segment- 

 alsirihige) discovered by Braun in Reptilia, and described at 



