AND ON THE DIRECT AGENCY OF THE SPERMATOZOON. 
241 
partial impregnation, while the yelks of the others were changing form and becoming 
irregular. But not a single embryo was produced. 
No. 5. Eighty-one eggs were obtained from another Frog, a few minutes after it 
had been killed by division of the spinal cord, and a portion of fluid which had been 
mixed with water twenty-four hours and a half, and kept in a temperature which had 
sunk from 54° Fahr. to 51°Fahr., but at the time the fluid was employed had again 
risen to 55° Fahr. — was supplied to them. 
This fluid on examination by the microscope was found to contain an abundance 
of spermatozoa, the whole of which were perfectly motionless, so that I was not able 
to detect even one which gave any sign of vitality. Yet the eggs in this experiment 
retained their natural healthy appearance for several hours ; but not one was im- 
pregnated, nor was even a single embryo produced. On the contrary, after thirteen 
hours, the yelks of some of them assumed a pyriform shape, while those of others 
became shrivelled and withered. 
No. 6. Thirty-six eggs were passed from a Frog, which had been killed about 
three-quarters of an hour, and some fluid which had been obtained and mixed with 
forty four hours before was shed over them, and pure water was then added. 
The envelopes of these eggs became expanded as under perfectly healthy and 
favourable conditions ; but within two hours of the contact of the eggs with the fluid 
the yelks of the whole became very irregular, shrivelled, and contracted, and assumed 
an appearance very similar to that which first results from the application of a strong 
solution of potass. Not one egg retained its spherical shape, but the whole entirely 
perished ; and it may be needless to add, not an embryo was produced. 
These facts then support the statement already made, that only while the sperma- 
tozoon continues to give evidence of vitality in its power of motion does it exert any 
fecundatory influence on the egg. They seem, too, to show that the period during 
which this vital force is retained by the mature spermatozoon alter it is passed from 
the body of the Frog is perhaps shorter even than what I have stated, and that the 
limit, in regard to time, depends much on physical influences. In addition to this, 
they seem to show that after all ocular evidence of power in the spermatozoon is 
lost, this body is inert, until decomposition has commenced, when its material con- 
stituents become injurious and destructive. 
The following experiments have more direct reference to the vitality of the egg, 
and appear to indicate that this is much longer retained than that of the spermato- 
zoon, and is less quickly affected by external causes. 
April 2, 1851. Atmosphere 55°. 
No. 1. Thirty-eight eggs were passed from a Frog killed twenty four hours and a 
half heiove, and some fluid which had been obtained and mixed with water about 
me hour and a quarter was then added to them. 
Segmentation commeneed in some of these eggs in eihoni four hours and a half , 
and on the seventh day eight embryos had been produced. 
