THE OVUM IN *rHE AMPHIBIA. 
213 
mode adopted in my experiments, it included a large proportion of developmental cells 
from which the spermatozoa escaped at longer or shorter periods after the fluid had 
been mixed with water, or had been retained for some time out of the body. I have 
very rarely found the seminal fluid of Rana temporaria obtained in the way stated, 
and at a temperature of about 50° Fahr., retain any impregnating influence for more 
than four or five hours. Thus, after mixing it with an equal proportion of water, very 
many of the spermatozoa have soon become motionless, and in less than two hours a 
moderate proportion only have continued active. At three hours there have been 
still fewer moving ; while at four hours the great majority of them have exhibited 
most unequivocal signs of lost vitality, being either extended at length or coiled 
on themselves (Plate XIV. fig. 8 c), as they usually appear when motionless, and adhe- 
rent to the surface of ova. If any, at this length of time, have been still moving in 
the fluid, they have been few in number, and their motions exceedingly feeble. Occa- 
sionally I have detected others, at this lapse of time, in the act of escaping from the 
cells (fig. 8 a and b), and these have always been the most energetic in their move- 
ments immediately after their liberation. Further, I have noticed that in those 
specimens of fluid which have contained most developmental cells, the spermatozoa 
have been longest in a state of activity. 
The following have been the results of observations on spermatozoa attached to the 
surface of ova, or contained in the water in which ova were immersed. At three-quar- 
ters of an hour after mixing recently obtained seminal fluid with the water and ova, 
vibratile spermatozoa have continued to be exceedingly abundant and in a state of 
great activity. At one hour and a quarter there were still an abundance in motion, 
but many were now perfectly motionless, and apparently dead. At one hour and a 
half I was not able to detect any movement in even a single spermatozoon out of a 
vast abundance which adhered to the surface of the gelatinous coverings of the ova, 
although I sought for this very carefully. Neither could I detect even the slightest 
indication of the spermatozoa having penetrated into these coverings, either near 
the surface or in the vicinity of the thicker envelope, which I regard as the chorion, 
and which immediately covers the vitelline membrane. After a lapse of some time 
all the appearance of spermatozoa on the exterior of the envelopes ceased. The 
longest period, after contact with spermatic fluid in water, at which I have hitherto 
been able to recognize these bodies on the surface of the frog’s egg has been six 
hours and one or two minutes, and about half an hour after segmentation of the yelk 
had commenced. This was on ova impregnated artificially, on the 14th of March, at 
a temperature of the atmosphere of the room of 54°‘5 Fahr. and 53°'5 of the water 
employed. A few motionless spermatozoa were then still found on the surface, but 
most of them appeared to be becoming disintegrated. The surface of the egg-envelope 
was then covered at places with numerous small granules, possibly the remains of 
spermatozoa which had disappeared. 
A somewhat similar result has ensued when spermatozoa have been two hours mixed 
