234 MR. NEWPORT ON THE IMPREGNATION OF THE 0\ UM IN THE AMPHIBIA 
a subsequent part of the same communication, these considerations are further 
referred to, as being those alone on which the transmission of structural peculiarities 
seemed likely to be explained*. 
Recent observation has now supplied to me a fact which renders these considera- 
tions, which heretofore were regarded as hypothetical, much more probable; but, at 
the same time, it necessitates a revision of the view that an impregnating influence is 
transmitted from the surface to the interior of the egg ; and also some correction of 
the deductions from experiment by which this view seemed to be supported. 
The fact referred to, is, that the spermatozoon of the Frog penetrates bodily into 
the substance of the thick envelopes of the egg, and comes into direct communication 
with, at least, the membrane which incloses the yelk in the interior. 
It’is my duty, therefore, to Science, and to the Royal Society, knowing this to be 
the case, to revise and to extend my views, and to submit them again to the Society 
in their amended form ; making, in self-correction, the certainty of fact now take the 
place of negative observation. 
In doing this, I shall endeavour to show, that, although still regarding the sperma- 
tozoon, for reasons to be adduced, as the organ of a special condition of force, or 
vitality in the male body, — its influence on the egg in fecundation is direct and 
immediate, and not operative, as heretofore supposed, merely through the envelopes: 
but, nevertheless, as I have before shown, that it is exerted only so long as the 
spermatozoon continues to give evidence of its vitality or force in its power oi 
motion. 
Before proceeding to show that the spermatozoon penetrates into the envelopes of 
the egg it is necessary that I should point out some of the conditions which aflfect the 
fulfilment of its fecundatory function, both in regard to the spermatozoon itself and 
to the ovum. These are, on the one hand, the persistence of vital power in the 
spermatozoon as influenced by the temperature of the surrounding medium ; and on 
the other, the endosmic property of the gelatinous coverings of the egg, and the 
susceptibility of the yelk which they inclose, to become impregnated. 
1. THE VITALITY OF THE SPERMATOZOON AND OVUM COMPARED. 
1. Of the Spermatozoon . — It has been elsewhere shown that when the mature 
spermatic fluid of the Frog has been more than four hours removed from the living 
body, and mixed with water, at a temperature of 50° Fahr. or but a few degrees 
higher, it usually has already ceased to have any power to fecundate the egg ; and 
its efficiency has been found to have been diminished in proportion to the length of 
time it has been obtained and so mixed. Nearly the whole of the observations 1 have 
since made have coincided with these results. Yet there have been two marked 
instances in which fecundation was effected by fluid, which had been obtained, and 
f Philosophical Transactions, 1851, p. 213. 
* Loc. cit, p. 56, 
