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



esculenta spawns at a higher temperature, and later in the season than the R. tempo- 

 raria, the subject of my observations, and that the fluid employed by PREVOST and 

 DUMAS, was always obtained, as they state, by vivisection, and was expressed from 

 the testes, and necessarily must have been in great part immature, and contained 

 many spermatozoal cells, from which the fecundatory agents were liberated at dif- 

 ferent periods during the observations, and thus appeared to show that the fluid 

 continues to be efficacious, at a high temperature of the atmosphere, for a much 

 longer period than is really the case. In my own experiments the fluid employed 

 being obtained, without vivisection, by simple compression of the body from the 

 seminal ducts and vesicles, has usually contained only perfectly mature and very 

 active spermatozoa, with but few cells of development. In this condition, as I have 

 stated, it has retained its fecundatory property only during the first three or four 

 hours. Yet, in the exception above mentioned, and also in the second one alluded to, 

 which occurred more recently, the fluid was efficacious at the end of twenty-four 

 hours in the first, and twenty-six hours in the second instance, the temperature being 

 similar on the two occasions. In both instances the fluid contained a very large 

 quantity of developmental cells, and had been procured from individuals which were 

 not fully prepared for the exercise of their fecundatory function. Further, I may 

 add, that in each of these instances, after the fluid had been supplied to some eggs 

 to test its effect, I found many undeveloped spermatozoal cells adhering to the 

 surface of the eggs, and detected some spermatic bodies in the act of being liberated 

 from them. These facts, then, are confirmatory of the suggestion respecting the 

 results obtained by PREVOST and DUMAS. 



The presence of undeveloped cells in the fluid obtained from the living Frog is 

 explicable in two or three ways: first, in that of the animal having but recently 

 been taken from its natural haunts, either early in the season, or at a later period, 

 after a continuance of unusually cold weather and easterly wind, or after the sexes 

 have but recently united ; in either of which cases, as also in certain others, in which 

 the individual itself has been late in the development of its reproductive organism, 

 developmental cells are thrown off from the testes together with already liberated 

 spermatozoa, and are usually abundant in the efferential ducts and vesicles. It may 

 thus be seen that in judging of the length of time during which the fluid preserves 

 its fecundatory influence, and consequently, the spermatozoon its vitality, after removal 

 from the body, it is necessary to take into consideration, not only the temperature 

 of the surrounding medium, but, also the precise condition of the fluid itself. In 

 perfectly natural impregnation by the Frog there is reason to believe that the fluid 

 contains but very few undeveloped cells, and that it is not employed until it has 

 acquired its full maturity, and that, as the time of its actual employment is exceed- 

 ingly brief, the oviposition of Rana temporaria occupying scarcely a single minute, 

 the retention of the impregnating influence and vital force of the spermatozoon may 

 be even for a much shorter space of time than I have mentioned from three to four 



