274 MR. NEWPORT ON THE IMPREGNATION OF THE OVUM IN THE AMPHIBIA 
to 65° Fahr., to afford a greater chance of success ; as all my previous experiments 
had shown that more eggs became fecundated at a moderately elevated, than, under 
otherwise similar circumstances, at a low temperature. The instant the object-glass 
(the half-inch of Ross’s microscope) was brought into focus, a vast quantity of sperma- 
tozoa were seen adhering to the surface of the egg at the part to which the pin’s head 
had been applied. Many of them, attached laterally to the surface, had already 
ceased to move ; others, only partially attached by their larger end, still vibrated the 
caudal or ciliated extremity rapidly, but did not appear to penetrate; while others, 
more ceotripetally attached by their body portion, vibrated the free extremity rapidly, 
and were seen in the act of gradually penetrating into the substance of the envelopes. 
I distinctly recognised one of these bodies which had just entered the envelope to a 
depth equal to about twice its own length, and when first seen had not reached so 
far as the middle or granulous layer of the envelope. Its motion was then slight y 
serpentine, and its course from without inwards was in a perfectly centripetal direc- 
tion, with its thicker or body portion extended forwards, and in a line with the 
centre of the yelk, its progress inwards, as seen beneath the microscope, being as 
continued and as direct as that of an arrow. I kept this object in focus for several 
seconds, and watched it through the granulous layer, but ultimately lost it m the 
more dense and, as yet, unexpanded portions of the inner layers of the envelope, 
after it had been distinctly seen by a friend, who was with me at the time of the ob- 
servation. A few seconds afterwards, as the envelopes became more expanded, very 
many of these spermatic bodies were seen to have already arrived at, and be in the 
act of passing through the inner or laminated portion of the envelopes,— the portion 
which, when the envelopes have acquired their full distension, by the imbibition ot 
water, is seen to be that which immediately covers the vitellary membrane. ^ A tew 
seconds later a great abundance of them were seen in contact with the vitellaiy 
membrane itself; and some were even partially imbedded by their thicker extremity 
in its substance, and some of these showed an appearance as if they were actually 
penetrating through it. But in no one instance could I then satisfy myself that the\ 
did really pass through ; since by alternately elevating and depressing the lens, and 
carefully noticing when the margin of the vitellary membrane was most distinctly 
defined, the appearances of perforation which some of them showed, seemed to be 
due to the spermatic bodies being imbedded in the membrane at some inclination to 
the plane of observation and to that of their direction being not quite centripetal. 
Yet there were other circumstances which seemed to show a likelihood that some 
spermatozoa do actually pass through the membrane. Thus, within the first fe\i 
minutes after the impregnating fluid had been supplied to the egg under observation, 
and at the time when the spermatozoa, which had penetrated its envelopes, weie fiist 
seen to have arrived at, and begun to enter the laminated portion, or zona pellucida, 
some of them were noticed to pass gradually onwards for a time, and then suddenly 
to disappear in an instant; as if, having passed into this tissue, they had also escaped 
