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



thus evident that an excess of fecundatory fluid is as unfavourable to the production 

 of the embryo as a deficiency. 



11. DEFICIENCY AND EXCESS OF FECUNDATORY INFLUENCE COMPARED. 



The results of these experiments with the fecundatory agent in excess require to 

 be further explained, and also to be compared with those obtained with deficiency of 

 the agent, in order that the nature of both may be properly understood. If this be 

 done it will be seen that fecundation of the frog's egg depends very much on the 

 physical influence of temperature ; and that this has a close relation with the intensity 

 of the force, or the degree of vitality evolved in the spermatozoon, at the time of its 

 application to the egg ; and probably also with the influence which the spermatozoon 

 supplies through a greater or less amount of material substance to the body to be 

 fecundated, at the time of its encounter, as in the following experiments made in 

 March 1852. 



The experiments by pin-point application of fluid show that only a very small 

 amount of influence is actually required to set up those changes in the yelk which 

 result in the formation of the embryo ; and other observations have convinced me 

 that the result is the more certain at a slight increase than at ever so slight a dimi- 

 nution of temperature. The effect of the application of minimum quantities is most 

 certain when the influence has only very recently been obtained, and consequently 

 while still endowed with its greatest degree of vitality. But even at that time a 

 given amount is required, and if such be not supplied the result is incomplete, and 

 partial fecundation only is effected. First then in regard to minimum quantities. 



Six eggs were placed each in a separate cell, and three of these were touched once 

 only with the pin-head loaded with fluid obtained about twenty-five minutes before, 

 while the other three were each touched once with the fine pin-point loaded in like man- 

 ner. Yet although there was only an interval of one minute between the application 

 of fluid to the two sets of eggs, two of the former by pin- head application had the 

 chamber developed, and segmentation commenced at the end of three hours and forty 

 minutes ; while one egg only of the three supplied by pin-point application began to be 

 segmented in three hours and forty-eight minutes, although the whole were placed under 

 precisely similar conditions in regard to light, heat, quantity of water and degree of 

 aeration. The third egg of the first set was not impregnated, neither were the two 

 remaining ones of the second set. Thus there was a difference between the two sets of 

 eggs, not only in the extent to which they were fecundated, but also in the rate of the 

 accomplishment of fecundation to the extent of eight minutes, in about three hours and 

 three-quarters. There was also a perceptible difference of time in the formation of the 

 respiratory chamber of the two, after the first hour, as was remarked by a distinguished 

 physiologist who was present with me when these comparative trials were made. The 

 two eggs of the first set, and the single egg of the second, which underwent seg- 

 mentation, afterwards produced embryos ; the remaining eggs were abortive. 



