THE OVUM IN THE AMPHIBIA. 
215 
ration either before or at the time of impregnation. With regard to the ovum of the 
Tritons, I have recently made the following observations, since becoming acquainted 
with the views of the authors named. 
A female Lissotriton punctatus, obtained on the l/th of May, produced several ova 
on the morning of the 19th. Cleavage of the yelk (which, I may remark, was entirely 
overlooked by Rusconi* in his account of the Newts) commenced in two of these ova 
at the expiration of eight hours, the temperature during the period having ranged from 
56° Fahr. to 62° Fahr. On examining these ova very carefully about an hour before 
the cleavage commenced, there were what I regarded as portions of the bodies of 
spermatozoa on the surface, but certainly no traces of any in the interior. While 
engaged in this examination the same female produced another egg, which she 
inclosed as usual in a folded leaf. On this specimen, examined at the end of half an 
hour, I could not detect any spermatozoa on the surface, which led me to imagine 
that it had not been impregnated, a supposition which ultimately proved to be correct, 
as no segmentation of the yelk took place in it. Some time after this, the tempera- 
ture of the atmosphere being 62° Fahr., I saw the same newt enclosing another egg in 
a leaf. This I immediately removed for examination, and thinking that this, like the 
previously deposited egg, had not been impregnated, no traces of spermatozoa being 
found on its surface, I placed it for about a minute in a small capsule filled with 
water, into which a quantity of fluid had just been expressed from a male that had 
been kept separate from the female. The fluid on examination was found to be com- 
posed almost entirely of very active spermatozoa. The egg was examined three 
minutes after immersion, and scarcely five minutes after it had been laid, and multi- 
tudes of spermatozoa were then seen adhering to its surface. Most of them were still 
vibrating rapidly, while others were motionless. But although I was able to distin- 
guish every part of these bodies, 1 could not detect any in the act of penetrating, or 
which had already penetrated into the substance of the envelope, and most certainly 
not one was imbedded in the interior. Neither were there any in contact with the 
yelk-membrane, or in the yelk-chamber of the envelope. 
The egg of the Newt is peculiarly fitted for an examination of this kind, from the 
fact of the existence of this yelk-chamber, or space in the interior of the envelope. 
This is formed by the gelatinous covering which the egg gains in the oviduct imbi- 
bing fluid by endosmose and becoming expanded immediately it comes into contact 
with water, when the inner layer separates from the vitellary membrane, with which it 
has been in contact within the duct ; and as the outer layers more and more expand, 
the yelk, covered only by the vitellary membrane, is left free in a large cavity in the 
interior, surrounded by a thin fluid. The spermatozoa of the Newts, as is well known, 
are of large size, and are easily recognized ; so that in the event of their having pene- 
trated the egg-covering before it leaves the duct, or at the moment of its expansion, 
or after the chamber has been formed in it, they can hardly escape observation. 
* Amours des Salamandres Aquatiques, 4to. Milan, 1821. 
