216 MR. NEWPORT ON THE IMPREGNATION OF 



I preserved this egg confined to one spot in a minute glass capsule, and in exactly 

 the same position beneath the microscope, for forty-eight hours. During the first 

 three quarters of an hour many of the spermatozoa on its surface exhibited as vivid 

 motions as at first, but still adhered to the same parts, and had not, so far as I could 

 perceive, changed their posture or their place in the least, or had penetrated in the 

 slightest degree into the envelope. At the end of twelve hours I found that the yelk 

 had undergone the usual process of cleavage, which, at that time, had already been 

 advanced to the stage of coarse granulation of the surface, a fact which proved most 

 distinctly that this egg had been impregnated. Spermatozoa were still distinctly 

 recognized over the whole surface of the envelope, but their motions had now ceased. 

 On the following morning, May 20th, the changes were found to have proceeded un- 

 interruptedly, as the yelk was then finely granulated over its whole surface. At a 

 little later period, the end of twenty -four hours, a few spermatozoa were still adhering 

 to the surface of the envelope, but the whole were perfectly motionless, and many 

 had evidently disappeared. Still, not one could be detected in the substance or in 

 the chamber of the envelope. At twenty-eight hours the granulation of the yelk was 

 nearly completed, and its surface was becoming smooth, and there were still a very 

 few motionless spermatozoa on the exterior of the envelope. At the end of forty-eight 

 hours, May 21st, I was still able to recognize the bodies of several spermatozoa which 

 had not yet disappeared, but which had become very indistinct, as if in a state of 

 diffluence. At the end of sixty hours I could no longer detect any trace of them. 

 The egg that was the subject of these observations proceeded regularly in its changes, 

 and ultimately produced the embryo ; all the stages of which I have traced and 

 delineated for future communication to the Royal Society. 



Subsequently to these observations I saw ova passed by another female, Lissotriton 

 palmipes, and on submitting these to the same close examination as the above, within 

 five minutes after their production, I again found what I regarded as the remains of 

 spermatozoa on the surface of the egg-covering, but not a trace of any in the in- 

 terior or in the vicinity of the yelk. 



Endosmosis of the envelopes during impregnation. But although the facts now 

 mentioned are so opposed to the view that the spermatozoa penetrate bodily into the 

 ovum, it is due to the distinguished observers to whom I have referred to enter some- 

 what more fully into the questions which their observations involve ; and while I am 

 free to admit the possibility of mistake or oversight on my part, to mention the 

 details of some experiments made expressly with the view to ascertain whether the 

 envelopes of the ovum of the Frog are permeable in any part to solid particles of 

 matter ; or whether there exists any orifice in them by which such particles can enter. 

 It is well known that during the transit of the ovum through the oviduct the vitellary 

 membrane becomes invested with a thick gelatinous covering, the first thick layer of 

 which may be regarded as the rudimentary chorion, and perhaps may be analogous 

 in its function, in some respects, as it seems to be in its place and mode of origin, to 



