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X. On the Impregnation of the Ovum in the Amphibia. {Second Series, Revised.) 
And on the Direct Agency of the Spermatozoon. By George Newport, F.R.S. 
F.L.S. 8sc. 
Received May 10, — Read June 17, 1852. 
Having shown in a former series of investigations, which has been honoured by a 
place in the Philosophical Transactions for 1851 , that the sole agent of impreg- 
nation of the ovum, in all cases of communion of the sexes, is the spermatozoon, — 
and having then supplied both direct and negative evidence that impregnation is not 
effected by the liquor seminis, — 1 endeavoured, in a subsequent communication to 
the Royal Society, in June 1851 *, to arrive at some knowledge of the manner in 
which impregnation is effected, and of the nature of the impregnating influence. 
Up to that period, and indeed, until very recently, I had never been able to detect 
any evidence of the existence of spermatozoa within the envelopes of the fecundated 
but had constantly found them in great abundance, and easily recognized, in 
contact with the exterior surface. Experiment also, made by immersion of the egg 
in coloured fluids, showed that the substance of the envelopes, although permeable by 
fluids, is uniform in its structure; but no evidence was afforded by it of any natural 
canal, fissure, or perforation through the envelopes of the egg of the Frog, capable of 
admitting the spermatozoon to the interior, as has been supposed to exist in the egg 
of the Mammalia-f-. 
Hence the conclusion which seemed to be fairly led to, was, that some influence 
was transmitted from the spermatozoon on the surface of the envelopes, through 
their substance, to the yelk which they inclose, — as the commencement of impregna- 
tion. But it was especially pointed out in my First Series;}:, that “simple contact of 
the spermatozoon does not appear to be sufficient to determine the transmission of 
more or less of the material structural characters of the male parent to the offspring 
and that, “possibly, we may hereafter find that the first changes induced by contact 
of the impregnating body are completed by its diffluence, and by the material con- 
stituents into which it is dissolved, being transferred to the yelk by endosrnosis 
Further, in my second communication, I remarked, — “I am not yet prepared to 
assent to the view, that simple contact alone, even of the spermatozoon, is sufficient 
to complete the changes which result in the formation of the embryo Again, in 
* Proceedings of Royal Society, vol. vi. p. 82. 
t Philosophical Transactions, 1840, p. 533, Plate XXII. figs. 165, 167. 
t Philosophical Transactions, 1851, p. 242. 
§ See “ Impregnation of the Ovum (Second Series),” June 19th, 1851, MS. No. 762, p. 49, in the Archives 
of the Royal Society. 
