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



Each cell was then filled with water, so that the egg which it contained was completely 

 immersed. Within the second minute after the eggs had been touched with the 

 loaded pin, there arose from each, at the point of contact, a microscopic bubble of 

 air, the egg which had been twice touched having two bubbles. These were found 

 by subsequent observations to be due to the circumstance of the eggs having been 

 exposed to the air, for a short time before they were touched, and their surface 

 become slightly dried, so that when the fluid was applied to it a small bubble of air 

 became involved and imprisoned in it, before the eggs were immersed in water. 

 This circumstance and its explanation are mentioned simply to show that the occur- 

 rence had no relation to the act of fecundation, as at first I had supposed was pro- 

 bable. 



I endeavoured to obtain some idea of the number of spermatozoa deposited from 

 the pin point, during its momentary contact with the egg, in these experiments. But 

 the result seemed to give but little hope that either of the experiments would be suc- 

 cessful, or that any fecundation could be effected by the application of so minute a 

 quantity of influence, as it was found that the number of spermatozoa deposited on 

 a plate of glass, beneath the microscope, when the pin point was applied to the glass 

 in the same way as to the egg, did not exceed from six to ten or twelve of these 

 bodies. Yet the results of the experiments were watched. Within the first half-hour 

 the eggs were removed from the temperature of 56FAHR. to one of 65FAHR. But 

 at the end of ten hours it was found that only in one instance had any fecundation 

 been effected. The grey central spot on the dark surface of the yelk was still pre- 

 sent in three of the eggs, and no respiratory chamber had been formed in either of 

 them. But partial fecundation had been effected in the fourth egg, which had been 

 twice touched with the loaded pin point. In this instance the dark surface of the 

 yelk was depressed, and the respiratory chamber had been formed between it and 

 the envelope, and two spherical opake white bodies appeared within it, lying side by 

 side on the middle of the surface of the yelk ; but no segmentation of this had taken 

 place, or even had been commenced. 



One cause of failure, in these first experiments, appears to have been the diminished 

 efficacy of the fluid, which had been obtained and mixed more than one hour before ; 

 as it will presently be seen that even a less proportion of the fluid sometimes is 

 effectual when employed immediately it is procured. 



As it was late in the season of last year when these experiments with minimum 

 quantities were commenced, the spawning of the frogs being then nearly at an end, 

 I was fortunate in procuring, on the second of April, a single unspawned pair of 

 frogs from their natural haunts, and thus was enabled to repeat the experiments with 

 the fewest disadvantages. This was done within four hours after the frogs were 

 captured. The fluid in this instance was very mature, was obtained in good abun- 

 dance, and was mixed with an equal quantity of water, and employed in the experi- 

 ments a few minutes afterwards. 



