238 MR. NEWPORT ON THE IMPREGNATION OF THE OVUM IN THE AMPHIBIA 



been liberated. There were, however, some of which the contents appeared to be 

 perfectly granular, and these I regarded as spermatozoal cells in the earlier stage of 

 development. 



The female with which this male had been paired was killed on the 4th, at the 

 time the experiments were to have been commenced. It was then found that the 

 eggs, like the fluid from the male, were immature. The whole of the eggs had escaped 

 from the ovaries into the cavity of the peritoneum among the viscera, and were 

 crowded together in a mass on each side, at the anterior part of the abdomen, and 

 were without any gelatinous covering. A few only had begun to enter the oviduct 

 on the right side of the body, and acquire their envelopes. In most of these eggs the 

 germinal vesicle had already disappeared. 



The fluid and eggs of the common Toad (Bufo vulgaris) are developed in precisely 

 the same way as in the Frog. On the 30th of March 1851, I examined the bodies of 

 a male and female Toad for the purpose of experiment. The great efferential ducts 

 and vesicles in the male were then entirely empty, no fluid having yet descended 

 into them. But the testes contained a vast quantity of spermatozoal cells, some of 

 which were distended by the spermatozoon, as if in the act of being liberated. But 

 not a single spermatozoon was free, or showed any sign of motion. The whole were 

 still immature, the caudal portion being as yet short and imperfect. 



In the female the ovaries were distended with eggs and occupied the whole of the 

 visceral cavity between the intestines. The eggs were of a sooty black colour, with 

 but a slight trace of the grey surface, and appeared to be nearly mature, but had not 

 yet left the ovary. The germinal vesicle of a large size, circular in its outline, and 

 somewhat flattened, still existed in nearly the whole of them. 



It is thus evident that the pairing of the sexes, both of Frogs and Toads, takes 

 place before the semen is fully matured, or the eggs have descended into the oviducts, 

 and that there is a near concurrence in the time of maturity in both. 



These facts seem to lead to the conclusion, that when, as in some of the fore-men- 

 tioned experiments, the male fluid contains a very large proportion of developmental 

 cells, which occasion its white appearance, it is not fully matured for its function ; 

 that the first portions of fluid which descend into the efferential vessels are usually 

 immature ; and that it is not absolutely necessary that the spermatozoa should be fully 

 formed before the cells escape from the testes. It seems fair then to infer from these 

 facts that the completion of the development of the spermatozoal bodies takes place 

 in the deferential vessels, or in the vesicles, perhaps in both : further, that the 

 quantity of fluid produced, when too great to be contained in the ducts, may become 

 accumulated in the vesicles, to be furnished at the instant it is required ; and that 

 there is a near concurrence in the time of maturity in the fluid in the male, and of 

 the eggs in the female, the former being only slightly in advance, in regard to time, 

 of the latter, at the natural period of their encounter ; a condition which perhaps 

 may be necessary to the full and healthy fecundation of the whole brood. 



