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



This result appeared to be far more inexplicable than any I had previously noticed. 

 A somewhat similar one had occurred once before, but I had attributed that to some 

 imperfection in the eggs employed, an explanation which did not apply in this case, 

 as eggs from the same female had all been fecundated in other experiments. 



Four eggs were then passed from another frog, immediately after death, each into 

 a separate cell, which was filled with a mixture of two parts of water and one of 

 seminal fluid, obtained only a few minutes before it was employed. Two of the eggs 

 were allowed to remain in this mixture in their cells, but the others, after a few 

 minutes' immersion, were well-washed, and supplied with pure water, and the whole 

 were then placed in a temperature of 60 FAHR. At the end of four hours I found 

 the surface of the first two eggs covered with an abundance of spermatozoa ; and a 

 chamber had been commenced, and the upper surface of the yelk was depressed, in 

 each, thus showing that some degree of fecundation had been effected, but no segment- 

 ation had taken place in either of these eggs at the end of Jive hours and a half', 

 although the temperature of the room had been raised during the interval from 

 60 FAHR. to 67 FAHR. The sixth hour was almost completed before either of these 

 yelks gave any indication of the probability of this change. Segmentation then com- 

 menced, but in a very irregular manner. In one egg the division was not in the 

 centre, but at the side of the yelk, and proceeded no further than to about one-half 

 the extent across the surface. In the other the surface of the yelk within the 

 chamber merely became sulcated twice in the same direction. Neither of these eggs 

 proceeded further with their changes, and of course no embryos were produced. 

 The two remaining eggs did not undergo any change whatever, and consequently 

 had not been impregnated. 



Although these failures were still attributed to some immaturity of the eggs, I 

 began to suspect that they might be occasioned by the immersion, or smothering of 

 the eggs in fluid of too great a density ; yet this suspicion appeared to be so hypo- 

 thetical as scarcely to merit consideration, when it was remembered that on a former 

 occasion when I had covered eggs with a solution of gum* and afterwards applied 

 the impregnating fluid to them, some of them became fecundated. I was well aware 

 that SPALLANZANI had found in his experiments that the greatest number of frogs' 

 eggs became fecundated when the fluid employed was very much diluted with water-f- ; 

 but I did not then know that M. QUATREFAGES had made an observation :}: which 

 completely coincided with the result obtained by myself. This acute naturalist found 

 that when he employed the pure semen of the sea-worms, the Hermella and the 

 Teredo, not a single egg was fecundated, and that when he mixed it with only a small 

 quantity of water, so as to obtain " un liquide tres opalin," that then only a very small 

 number of eggs showed any traces of fecundation. He ascribed these results simply 



* Philosophical Transactions, 1851, p. 236. t Dissertations, vol. ii. p. 190. 



t Annales des Sc. Naturelles, 3 me Serie, torn. xiii. p. 129. 



