236 MB. NEWPORT ON THE IMPREGNATION OF THE OVU.M IN THE AMPHIBIA 
esculmta spawns at a higher temperature, and later in the season than the R. te,npo. 
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 feeundatory 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, foi a muc 
longer period than is really the case. In my own experiments the fluid employed 
being obtained, without vivisection, by simple compression of the body fiom the 
seminal ducts and vesicles, has usually contained only perfectly mature and leit 
active spermatozoa, with but few cells of development. In this condition, as I hare 
stated, it has retained its feeundatory property only during the first three or our 
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-jour 
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 contamed a very large 
quantity of developmental cells, and had been procured from individuals which were 
not fully prepared for the exercise of their feeundatory 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. . ■ t. 
The presence of undeveloped cells in the fluid obtained from the living lOg is 
explicable in two or three ways: first, in that of the animal having but recently- 
been taken from its natural hauuts, either early in the season, or at a later perio , 
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 vesicies. It may 
thus be seen that in judging of the length of time during whicli the fluid preserves 
its feeundatory influence, and consequently, the spermatozoon its vitality, after remova 
from the body, it is necessary to take into consideration, not only the teniperatiire 
of the surrounding medium, but also the precise condition of the fluid itse . n 
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 Rnna femporaria occupying scarcely a single ininiite, 
the retention of the impregnating influence and vital force of the spermatozoon iiiay 
be even for a much shorter space of time than I have mentioned— from three to four 
