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. 
