1885.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 139 



receive tbe elements of its growth from the interior of the ovary, and 

 that it must be furuisbed with organs of absorption and respiration 

 suited to the medium in which it is developed. A large supply of nour- 

 ishment must evidently be required, as the ovary contains frequently 

 forty or fifty young fish, which, when fully developed, measure more 

 than 2 inches in length, and which together will weigh from one-twelfth 

 to one-sixteenth as much as the i)arent fish. The ovary consists of a 

 membranous bag partially divided at the upper (anterior) part, and 

 terminating below in a nanow canal, which, in some species, opens ex- 

 ternally in a cloaca common to it, and the urethra in others by a sepa- 

 rate opening situated between the anus and urethra. The sac has 

 three coats — a peritoneal, a muscular, and a mucous. The mucous 

 layer is thrown into a number of longitudinal folds, and on the inner 

 surface of the ovary the ova are found ; and as the fretal fish grows 

 these folds extend so that each ftetus is in contact by each of two sur- 

 faces with the mucous membrane. The organ is well supplied with 

 blood-vessels, an artery entering at each horn of the ovary. They arise 

 from the aorta immediately after the union of the branchial arteries, and 

 at the latter end of gestation each is larger than the descending aorta. 

 The posterior part of the uterus (ovary) also receives vessels from the 

 abdominal aorta. In the early stages of development the foetus is 

 embedded in a very tenacious secretion, which resembles para-albu- 

 men in that it can be drawn out into threads of a foot or 18 inches 

 long. As gestation advances the secretion of the ovary becomes more 

 fluid, and its quantity is increased so that as much as three drams 

 can be obtained from one ovary towards the end of gestation. It then 

 forms an opalescent fluid, specific gravity, 1.025 ; does not coagulate on 

 heating ; acetic acid throws down a white precipitate, mixed with equal 

 parts of distilled water, and filtered, it has no action on polarized 

 light; heated in an open vessel, a pellicle forms on the surface. It 

 probably contains some albumen-compound, fat, salt, phosphates, and 

 iron; but it has not been submitted to a careful analysis.* The foetus 

 during the earlier stages of its development goes through changes ap- 

 parently analogous to those which take place in the ova of oviparous 

 fishes, and it is not until the fins are formed that any departure from 

 the ordinary plan shows itself. As soon as the fins were well fortned 

 the dorsal, caudal, and ventral (anal). fins became edged with a delicate 

 membrane fortned apparently entirely of cai)illary blood-vessels. As 

 the foetus grows this membrane is split uj) into processes or digitat:ons, 

 which extend a considerable distance beyond the margin of the fin, 

 sometimes as much as a quarter of an inch. They retain the same 

 structure during the whole period of development, and are so extremely 



* This fluid is usually expelled frora the ovary by the struggles of the fish wheu 

 taken from the water, so that it is extremely rare to find one in our market in -which 

 the membrane closing the orifice of the ovary has not been ruptured. This is proba- 

 bly' the reason that it has not been already noticed. 



