280 MR. NEWPORT ON THE IMPREGNATION OF THE OVUM IN THE AMPHIBIA 



it may yet be thought to be induced by some attractive power in the substance of 

 the yelk itself; and that, therefore, the entrance of the spermatozoon may be as much 

 due to the egg as to any power of motion in the penetrating body. An accident has 

 enabled me to test the validity of this surmise. 



I had promised to show the fact of penetration to a friend, but circumstances pre- 

 vented me from doing so until the season had nearly passed, and the whole of my 

 frogs had spawned. I determined therefore, as a last resource, to endeavour to ob- 

 tain some fecnndatory fluid from a male which had already paired two or three days 

 previously, and to employ it with the only eggs I had then left, which remained in 

 the body of a frog that had been killed twenty-six hours before, and which, as former 

 experiments had shown, it was probable had lost their vitality. The fluid required was 

 obtained with ease, but mixed with a large quantity of spermatozoal cells. This was 

 supplied to some eggs from the dead frog, since, although I did not expect that the eggs 

 would be fecundated, I hoped for an opportunity of again witnessing the penetration 

 by the spermatozpon. The spermatozoa in the fluid obtained were very active, and 

 fully efficient, and were supplied in abundance to several eggs in separate cells under 

 the microscope. The envelopes of the eggs expanded as usual, and endosmosis went 

 on in a perfectly natural way, and an abundance of spermatozoa adhered to their 

 surface. At the expiration of from fourteen to twenty minutes I found that several 

 spermatozoa had penetrated the envelopes and were adhering in the usual way to 

 the vitelline membrane. In one egg there were six, in another five, and in a third 

 four, distinctly visible in the plane of observation that could be brought at once 

 within view with the microscope, besides others recognisable on changing the focus. 

 It was thus evident that spermatozoa, even of the previously paired Frog, still retained 

 their power of penetrating into dead eggs, as these ultimately proved to be, after 

 careful preservation to the sixth day in a favourable temperature. The spermatozoa 

 were distinctly visible within the envelopes, without change of position, for several 

 hours, but no fecundation was effected by them ; no chamber was formed in either 

 of the eggs, no segmentation took place, nor was any embryo produced. These 

 circumstances seem to show that the eggs were already dead, as was supposed, before 

 contact of the spermatozoon ; consequently that the entrance of the spermatozoon 

 into the envelope is due to a power inherent in the penetrating body, and not simply 

 to an attraction on the part of the yelk; although from the fact that the spermatozoa 

 usually enter in a centripetal direction, it is probable that some influence may be 

 exerted by the yelk or its vesicle, although penetration is mainly the result of force 

 in the spermatozoon. 



The facts now stated of penetration by the spermatozoon seem to lead us better 

 to understand the nature of some experiments with solutions of caustic potass, which 

 are detailed in my former paper. I have repeated these experiments, during the past 

 season, in the presence of several friends, Professors SHARPEY, ELLIS, and BELL, and 

 Messrs. BUSK, TOMES and WATERHOUSE, with results precisely similar to those which 



