218 
MR. NEWPORT ON THE IMPREGNATION OF 
also quitted the ovarium, but the whole on that side had passed into the oviduct in the 
usual way. The eggs found in the cavity of the body consisted only of yelk-masses 
in their vitelline membranes. I immediately placed some of these eggs in water, with 
seminal fluid obtained from the male with which this female had been paired ; but 
not a single egg became impregnated, or gave afterwards any sign of formation of 
the embryo. I had some hesitation in regarding this experiment as quite conclusive, — 
that impregnation cannot take place before the egg has gained its gelatinous envelope, 
and consequently while it is still within, or has but just escaped from the ovary, — 
from the possibility that these eggs might have been for some time in the cavity of the 
body, and that some change might have been induced in them through long deten- 
tion. In so far, however, as that this was in accordance with Spallanzani’s experi- 
ment, it seemed to point to the nature and importance of the covering which the 
egg gains in the oviduct. 
Since my attention has been more particularly directed to this point of investi- 
gation, I have repeated the experiment on the ova of the Newt, Lissotriton palmipes, 
with precisely similar results. I opened the body of a female with great care (after 
dividing the spinal cord through the medulla oblongata), for the purpose of ob- 
taining ova from the oviducts, for artificial impregnation, and immediately saw that 
a number of ova were free in the cavity of the abdomen, and were in the course of 
being transferred to the entrance of the tubes, as stated in the first part of this paper. 
These ova, like those which had recently escaped from the ovarium in the Frog, were 
without any other covering than their vitelline membranes ; most certainly I was 
unable to detect any other, and they were so delicate that it was with difficulty they 
were removed into water to which fluid from the male had been added. But 
although uninjured in the removal, and in every way carefully treated, not one gave 
any sign of cleavage of the yelk, which, as I have before stated, I have constantly 
found take place in the impregnated ova of newts as well as of frogs, although the 
fact of its occurrence was overlooked by Rusconi ; not one egg afterwards produced 
the embryo. Thus then it seems fair to conclude that the egg in the Amphihia is 
not fitted for impregnation until after it has entered the oviduct and acquired its 
gelatinous covering. 
I have already shown that there is a remarkable coincidence between the rate of 
expansion of the gelatinous covering, immediately after the egg is placed in water, 
and the susceptibility of the egg to become impregnated ; and that in proportion as 
the covering becomes enlarged and distended by imbibition of water, the susceptibi- 
lity of the egg becomes diminished ; until at the end of about half an hour it is 
almost completely lost, at which time the rate of expansion of the envelope is also 
greatly lessened, and the envelope itself has attained to more than two-thirds its future 
diameter. Now Spallanzani found that the susceptibility of the ovum, when im- 
mersed in water, had ceased at the end of fifteen minutes, at which time the envelope 
is considerably enlarged. Prevost and Dumas also observed that the expansion of 
