268 MR. NEWPORT ON THE IMPREGNATION OF THE OVUM IN THE AMPHIBIA 
while viewing the egg, instead of the observation being made through the double 
medium of air and water. This was the method of examination m all the subsequent 
''’'Thrap''pearance which first led me to suspect that spermatozoa do penetrate into 
the envelope, was produced by an acicular body, which seemed to have its narrowed 
extremity in near proximity to the vitelline membrane. The direction of the longi- 
tudinal Lis of this body was in a line with the centre of the yelk. But what appeared 
to be its larger end was farthest removed from the yelk; and this circumstance 
seemed to show that the appearance could hardly be due to the presence of a sper- 
matozoon, which, if the observation were correct, must have penetrated in a direc- 
tion the reverse of that of its usual motion. ^ i ^ Ko 
It was necessary, therefore, that the suspicion raised by this observation should be 
settled I had again and again found, as before shown, that the egg of the frog may 
be impregnated, under certain conditions, by the direet application of spermatozoa 
to almost any part of its surface, and this enabled me to put the question of penetra- 
tion to the test. In the first trial, an egg was placed in a single cell, and immerse 
in water for one minute— the water was then removed, and the egg touched on oiie 
point only of its surface with the head of a pin, loaded with the fecundating ui , 
which had been obtained and mixed with water about two hours before. I had ex- 
pected that on watching the egg beneath the microscope, from the instant of con act 
with the pin's-head and the re-filling of the cell with water, to have been able to 
detect the spermatozoon during its passage through the envelope. But this 1 taile 
to do, in the present instance,— no spermatozoa were detected m the interior ot the 
envelope, although many were easily observed on the surface at the pomt to whic i 
they had been applied by the pin. Yet, this egg, placed in a temperature of 66 F.vhb., 
underwent segmentation in three hours and thirty-two minutes, and ultimately pro- 
duced an embryo. A similar trial was made, at the same time, with an isolated egg 
after immersion for two minutes in water, which was then withdrawm, and the fecun- 
dating fluid applied as before. In this instance, several spermatozoa had penetratei 
for a short distance into the envelope, but had not reached the covering "'“C ’ 
diately invests the yelk. No respiratory chamber was formed above the ye in ns 
ego- nor was any embryo afterwards produeed. In a third instance, with an egg, 
which had been immersed tor Jive minutes, the experiment was equally unsuccessfu . 
On the 24 th of March a further trial was made with an isolated egg, aftei one minu 
immersion. The fecundating fluid employed had been obtained only sixteen minutes 
before it was used, and was applied by the head of a pin, once only, to one point o 
egg In this case, at the expiration of half an hour, I distinctly saw a single sperma- 
tozoon sticking by its larger extremity into the vitelline membrane, and a "»nutes 
later there was evidence of the respiratory ehamber being about to be forme . 
egg underwent segmentation, and afterwards produced a good embryo. In a second 
egg immersed for three minutes, and in a third for>e iiii/mfes, there were no appear- 
