218 MR. NEWPORT ON THE IMPREGNATION OP 



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 Amphibia 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 



