THE OVUM IN THE 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, arid 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 u 

 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 0> 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 





