240 MR. NEWPORT ON THE IMPREGNATION OF THE OVUM IN THE AMPHIBIA 
mersed in water after expulsion from the body. The length of time during which 
they are susceptible of impregnation has relation to each of these conditions ; and 
these have now acquired additional interest in the establishment of the fact that the 
spermatozoon penetrates into the envelopes of the eggs, and that, consequently, the 
rate of expansion of the envelopes has a further direct relation to its function. 
The following experiments will illustrate the foregoing observations:— 
It may here be remarked, that although, as in my former paper, the date of the 
experiment is recorded, it is so only for the convenience of reference, and not with 
any regard to priority of period at which the experiments were made ; the details 
being given only in illustration of the general statements enunciated. 
April 2, 1852. Atmosphere 55° Fahr. The first three of the following experiments 
were made with the eggs and fluid from a pair of Frogs which had been obtained 
from their natural haunts only three hours before the female was killed, by division 
of the spinal cord, for the purpose of the experiments. 
No. 1. Eighty-six eggs passed from the Frog at one hour and a half after death, 
were supplied with fluid from the male with which this female had been paired, — the 
fluid having been obtained and mixed with water one hour and a before it was 
employed. 
On the seventh jifty-two embryos had been produced from these eggs, and 
some of them were then escaping from their envelopes. 
No. 2. Thirty-seven eggs, obtained from the same female, were supplied with a 
portion of the same fluid as the above, after it had been mixed with water about tu'o 
hours and three-quarters. 
Twenty-eight embryos were produced from these eggs at the same time as the 
above. 
No. 3. Sixty eight eggs from the same Frog at six hours and three-quarters after 
death were immersed in the same portion of mixed fluid and water in which the eggs 
of No. 2 had been fecundated. In this experiment the fluid had been six hours and 
three-quarters mixed with water. 
At the end of three days the eggs still had a healthy appearance, but on the seventh 
day not one had given any evidence of having been impregnated, nor was any 
embryo ultimately produced. Thus the fluid had lost its fecundatory property, at u 
temperature of 55° Fahr. between the end of the third and of the seventh hours. 
As it was possible that the failure in this experiment was due as much to the eggs 
as to the fluid employed, it having already been shown that impregnation is some- 
times effected with fluid which has been twenty-four hours removed from the body, — 
the following experiments were then made : — 
No. 4. Sixty-nine eggs obtained from the same female at one hour and twenty 
minutes after death were bathed with fluid procured from another male, and which had 
been mixed with water thirty hours previous. These eggs preserved their regularity 
of outline for nearly six hours, at the end of which time one egg showed traces of 
