BULLETIN OF THE UNITED STATES FISH COMMISSION. 93 



The individual embryos were slender, about six millimeters long, 

 with a pigmented stripe on the posterior dorsal part of the yelk-sack 

 and along the upper margin of the hinder half of the tail. A large 

 yellowish oil-drop occupies an anterior jiosition in the yelk substance. 

 The caudal part of the tail fold is already widened, as in the embryos 

 of clupeoids, and the end of the straight chorda, as in the latter, divides 

 The tail into very nearly equal dorsal and ventral moieties. The eyes 

 were fully pigmented and black, and what pigment cells were present 

 on other parts of the body were stellate, with several rays running out 

 from a nearly colorless center, in which the nucleus lies embedded. 



The only paired fins developed are the pectorals; no traces of the 

 ventrals are yet visible. The proportions of the embryos are nearly 

 those of the clupeoids, the head being but slightly more robust. The 

 majority were found to be coiled up, or with the tail thrown around to 

 one side over the yelk-bag and head, as they lie in the ovary. Each 

 embryo as coiled up formed a flattened oval body nearly one and a half 

 millimeters long and one millimeter wide. Some of these coiled ones 

 seemed also to be covered by an exceedingly thin membrane, which is 

 supposed to represent a zona radiata or egg-membrane. Fragments of 

 this membrane enveloping the embryos when examined under a high 

 power, however, failed to show the presence of fine perforations or pore- 

 eanals. These membranes were, moreover, in many instances, adherent 

 to the vascular processes depending from the roof of the ovary, and it 

 is inferred, therefore, that the membranes mentioned are actually the 

 vestiges of a very thin egg-capsule. 



The ovary itself was found to have very thin inferior and lateral walls, 

 which were somewhat colored by dark pigment. These thin walls are 

 not concerned in the development of the ova at all; the latter in fact 

 are developed in the thickened dorsal or mesoilietric side of the ovary, 

 which is highly vascular. When the ovary is opened and the embryos 

 shaken out, it is found that there is an abundant covering of flat, fleshy 

 processes which arise from the roof of the ovarian cavity. The basal 

 part of these processes is thickened, traversed by vessels, and consists 

 largelj" of ovarian stroma, in which immature eggs are found embedded 

 in various stages of growth. The distal part of the processes which 

 depend into the ovary are subdivided into slender digitations, which 

 dip down amongst the great mass of embryos. These terminal digita- 

 tions, upon cutting sections of them, are found to be highly vascular; 

 small vessels in fact comprise the greater part of their substance. The 

 vessels which traverse the digitations evidently form long recurrent 

 loops and serve to bring the oxygenated blood of the parent female fish 

 into close relation with the embryos or foetuses, since these digitations 

 pass down between and amongst the embryos lying in the ovarian bag, 

 in such a way that few of them can escape coming into direct contact 

 with some of the vascular loops in the digitations. The latter also 



