OVARIAN STRUCTURES OF VIVIPAROUS BLIND FISHES. 49 



In the ovary of the pregnant female E, whose young were 

 almost ready for birth, the ovisac is thinner than in the case just 

 described. The different cell-layers can scarcely be distinguished, 

 though where the cells themselves are visible, the nuclei in section 

 have the rod-like form mentioned above. The capillaries have 

 mostly disappeared, apparently being closed by the crowding to- 

 gether and stretching of the cellular structure ; but in places one 

 comparatively large vessel appears, containing two or more rows 

 of corpuscles, side by side. At this place the wall is enlarged 

 somewhat to accommodate the vessel. 



In the ovary of C, which contained ova quite well advanced, 

 the ovisac is very similar to that described for D. But in some 

 portions of this ovary the muscle layer is restricted almost 

 entirely to longitudinal fibers, the transverse layer being much 

 reduced. Capillaries penetrate freely through these muscle 

 layers in all directions ; those in the lining epithelium are larger 

 than those in the other specimens already described. 



In the ovary of B the ovisac is similar to that in C, but the peri- 

 toneal covering is not so distinct ; there is the same arrangement 

 of muscle-fibers - - the outer longitudinal and the inner transverse, 

 the latter being much the deeper. The innermost epithelial layer 

 is composed of " pavement " cells with quite large distinct nuclei. 

 Numerous capillaries are found in this inner lining. 



Compare in this connection Eigenmann's description of the 

 ovarian wall in Cymatogaster (op. cit., p. 418) : 



" The ovarian walls are composed, first, of the thin peritoneal 

 membrane ; second, of a layer of longitudinal muscle fibers ; 

 third, of a layer of circular muscle fibers, inside of which there is, 

 in places, a layer of longitudinal fibers ; fourth, of a very thin layer 

 of cells with flattened, deeply stainable nuclei ; fifth, of a layer of 

 epithelium. This layer is derived from the peritoneum." 



Stuhlmann found the ovarian wall in Zoarces to have a toler- 

 ably deep, non-striated, muscle layer, the fibers of which were 

 closely packed together next to the peritoneal covering, but 

 toward the lumen they were split apart by numerous sinuses 

 containing blood vessels. The oviduct was similarly composed, 

 except that there were few if any clefts between the fibers and 

 there were fewer blood vessels. 



