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 mu^c 
due to the egg as to any power of motion in the penetrating bod}. An acci ent as 
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 fecundatory 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 Ihis wa, 
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 spermatozoon. 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 then- 
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 m a tliii 
four distinctly visible in the plane of observation that could be brought at once 
within view with the microscope, besides others recognisable on changing tie ocus. 
It was thus evident that spermatozoa, even of the previously paired Frog, still retained 
their poicer of fenetrafmg 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 eit lei 
of the eggs, no segmentation took place, nor was any embryo produced Ibese 
circumstances seem to show that the eggs were already dead, as urns 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 simplv 
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 oeite 
to understand the nature of some experiments with solutions of caustic potass, w iic i 
are detailed in my former paper. I have repeated these experiments, during the past 
season, in the presence of several friends. Professors Sharpe y, Elus, and Bell, and 
Messrs. Busk, Tomes and Waterhouse, with results precisely similar to those whic 
