198 
MR. NEWPORT ON THE IMPREGNATION OF 
the removal from low to high temperature was within the first half hour ; while it did 
not occur, in the only experiment in which it happened in Set F, No. 1, until the end 
of sir hours and a-half, when the removal from a similar low to a like high tempera- 
ture was not made until one hour and a half after impregnation. 
The influence of temperature is thus as marked in its effects on the impregnation 
of the ovum as it can be proved to be on the future development of the embryo. 
Impregnation is accelerated, and also is more certain in its occurrence in a high 
than in a low temperature. In the latter it becomes retarded and is less determined. 
This applies equally to the susceptibility of the ovum, and to the fitness of the im- 
pregnating fluid to effect impregnation. But in proportion as this fitness is exalted 
by increase of temperature, so is the duration of the capability to receive in the one, 
and the efficiency to communicate in the other diminished. Spallanzani found that 
the ova of toads placed in an ice-house could be impregnated at the end of forty-one. 
hours*. Prevost and Dumas'!- mention that they were successful, and that too 
to a great extent, with ova that had been twenty-four hours in water, the temperature 
during the period ranging from 18° Cent. (64°‘4 Fahr.) to 22° Cent. (71°'6 Fahr.), and 
with some eggs that had not been immersed even at thirty- six hours:}:, the temperature 
being then from 12° Cent, to 15° Cent. (53°’6 to 59° Fahr.). The results obtained by 
myself have been much less successful. Out of one hundred and forty ova obtained 
from a female frog, killed twenty-four hours before and preserved at or below the tem- 
perature of 55° 5 Fahr., at which the experiment was made, only a very few became 
partially segmented, but not one produced an embryo ; although an abundance of im- 
pregnating fluid, abounding with spermatozoa, and obtained only a few minutes before 
it was employed, had been supplied to them. It is evident therefore that this failure 
was due chiefly to the ova, and not to inefficiency of the impregnating fluid. On the 
other hand, I have been equally unsuccessful with ova from a frog that had been 
killed only two hours and a half when the impregnating fluid employed had been 
snore than four hours and a half mixed with water. In this case the failure appeared 
to have been due chiefly to the spermatozoa, nearly the whole of which, on inspection 
by the microscope, were found to be motionless and appeared to have lost their vita- 
lity. At the same titne it must be mentioned that the female from which the ova 
employed in No. 3 of the last set of experiments were obtained still existed, in so far 
as the vitality of the muscular system was concerned, and therefore can hardly be 
mentioned in comparison with MM. Prevost and Dumas’ observation. But while the 
numerical results obtained by myself have been less favourable than those of Spal- 
lanzani or the physiologists now mentioned, the general facts, so far as they are open 
to comparison, are in full accordance with them. The difference in the details of 
our respective observations appears to have been due in chief part to the influence of 
temperature at the time of the impregnation of the ova, or within the first two or 
three hours after the impregnating fluid has been supplied. Thus, if the temperature 
* Dissertations, &c., vol. ii. p. 177. f Loc . cit ., vol, ii. p. 140. + Id ., p. 134. 
