204 WILLIAM WALLACE. 



• 



(1901) confirms the observatioUj adding that karyokinesis of 

 these cells may also occasionally occur. Beyond the fact of 

 the enlargement of the follicular epithelial cells, the ruptured 

 follicle of the Teleostei bears little resemblance at any stage 

 of its development to the complicated structure known as the 

 corpus luteum in mammals. Cunningham's (1897) observa- 

 tions on this head appear to be quite accurate. An approach 

 to the mammalian condition is, however, not wanting in the 

 case of the elasmobranch fishes (figs. 31, o2), as Giacomini 

 (1896) has already shown. 



My material for the study of the corpus luteum in 

 Spinax niger is limited to two ovaries. These represent 

 two distinct stages in the " adult cycle " of the organ. One 

 ovary was that of a female in which ovulation had just 

 occurred; the ova had just descended into the oviduct. Six 

 corpora lutea were present in this ovary, corresponding to 

 the number of eggs in the oviduct. The original openings 

 of these follicles to the exterior had closed up. P^rom a com- 

 parison of the size of these corpora lutea with that of a ripe 

 ovum it is clear that a very considerable contraction of the 

 follicle has taken place after rupture. The wall of the 

 follicle which is opposite to its area of attachment to the 

 ovary is folded inwards, doubtless by the force of the con- 

 traction. On sectioning the corpus luteum at this stage we 

 find a considerable cavity more or less filled with a staining 

 plasma of some sort, pi'obably the liquor folliculi. The 

 wall of the follicle is composed of three well-defined layers — 

 endothelium, theca, and follicular epithelium. The endothe- 

 lium is a single layer of uniform cells. The theca is a thick 

 and very dense stratum of fibrous connective tissue. Towards 

 the inside of this layer the cells and fibres are more loosely 

 arranged, and venous blood-vessels with very thin walls, and 

 of various sizes and shapes in section, are present. This layer 

 abuts internally on the membrana propria folliculi, 

 which in turn surrounds the follicular epithelium. The con- 

 dition of the latter is very renuirkable. It forms a thick 

 lining to the cavity of the follicle, and is several cells in thick- 



