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



while viewing the egg, instead of the observation being made through the double 

 medium of air and water. This was the method of examination in all the subsequent 

 experiments. 



The appearance which first led me to suspect that spermatozoa do penetrate into 

 the envelope, was produced by an acicular body, which seemed to have its narrowed 

 extremity in near proximity to the vitelline membrane. The direction of the longi- 

 tudinal axis of this body was in a line with the centre of the yelk. But what appeared 

 to be its larger end was farthest removed from the yelk ; and this circumstance 

 seemed to show that the appearance could hardly be due to the presence of a sper- 

 matozoon, which, if the observation were correct, must have penetrated in a direc- 

 tion the reverse of that of its usual motion. 



It was necessary, therefore, that the suspicion raised by this observation should be 

 settled. I had again and again found, as before shown, that the egg of the frog may 

 be impregnated, under certain conditions, by the direct application of spermatozoa 

 to almost any part of its surface, and this enabled me to put the question of penetra- 

 tion to the test. In the first trial, an egg was placed in a single cell, and immersed 

 in water for one minute the water was then removed, and the egg touched on one 

 point only of its surface with the head of a pin, loaded with the fecundating fluid, 

 which had been obtained and mixed with water about two hours before. I had ex- 

 pected that on watching the egg beneath the microscope, from the instant of contact 

 with the pin's-head and the re-filling of the cell with water, to have been able to 

 detect the spermatozoon during its passage through the envelope. But this I failed 

 to do, in the present instance, no spermatozoa were detected in the interior of the 

 envelope, although many were easily observed on the surface at the point to which 

 they had been applied by the pin. Yet, this egg, placed in a temperature of 66 FAHR., 

 underwent segmentation in three hours and thirty-two minutes, and ultimately pro- 

 duced an embryo. A similar trial was made, at the same time, with an isolated egg 

 after immersion for two minutes in water, which was then withdrawn, and the fecun- 

 dating fluid applied as before. In this instance, several spermatozoa had penetrated 

 for a short distance into the envelope, but had not reached the covering which imme- 

 diately invests the yelk. No respiratory chamber was formed above the yelk in this 

 egg, nor was any embryo afterwards produced. In a third instance, with an egg, 

 which had been immersed {or Jive minutes, the experiment was equally unsuccessful. 

 On the 24th of March a further trial was made with an isolated egg, after one minute's 

 immersion. The fecundating fluid employed had been obtained only sixteen minutes 

 before it was used, and was applied by the head of a pin, once only, to one point of the 

 egg. In this case, at the expiration of half an hour, I distinctly saw a single sperma- 

 tozoon sticking by its larger extremity into the vitelline membrane, and a few minutes 

 later there was evidence of the respiratory chamber being about to be formed. This 

 egg underwent segmentation, and afterwards produced a good embryo. In a second 

 egg immersed for three minutes, and in a third for Jive minutes, there were no appear- 



