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IX. On the Impregnation of the Ovum in the Amphihia. (First Series.) 
By George Newport, F.R.S., F.L.S. 8^c. 
Received June 20, — Read June 20, 1850. 
The communication which I have now the honour to present to the Royal Society 
is a portion of a series of investigations on the Development of the Embryo on which 
I have been for some years engaged, and which was commenced in a paper on the 
Development of the Myriapoda, that was honoured with a place in the Philosophical 
Transactions for 1841. I now propose to give the results of my observations on the 
Amphibia, reserving to a future early occasion the continuation of those on the Inver- 
tehrata commenced in the paper alluded to. 
The Amphibia, of all the vertebrated animals, afford to us the readiest means of 
investigating the difficult subject of Impregnation by actual experiment, and it is 
only, perhaps, by combining experiment with careful observations on the physical 
conditions that affect the development of the germ, and comparing these with the 
facts of the natural history and instincts of the species, that we may hope, ulti- 
mately, to obtain some further insight into this one of Nature’s most hidden secrets. 
I shall endeavour, therefore, in this communication, to show the condition of the 
ovum in the Amphibia through its earliest changes, and also before and immediately 
after impregnation, and to detail experiments made with a view to learn by what 
means its fecundation is effected ; — and in a future communication I propose to trace 
the development of the embryo from the time of fecundation to that of its liberation 
from the ovum, in the two chief divisions of the class, — the tailless and the tailed 
Amphibia. The subjects thus naturally form two series — Impregnation and De- 
velopment. 
IMPREGNATION OF THE OVUM. 
The history of what we can now prove to be the agent of impregnation, the sper- 
matozoon, deserves to be especially noticed. Although great attention has been paid 
by physiologists during the last thirty years to almost every point of inquiry connected 
with the production and physical composition of the seminal fluid of animals, and its 
relation to the fecundation of the ovum, we have remained to the present time without 
« 
any acknowledged proof either of the part which the different constituents of this 
fluid take in impregnation, or of the mode in which it effects impregnation. This 
perhaps is little to, be wondered at when we remember how many years elapsed before 
the great discovery of Ham and Leewenhoek of the existence of moving bodies in 
the fluid, as part of its normal composition, was admitted. It is now one hundred 
and eighty-three years since Leewenhoek communicated the important discovery 
MDCCCLI. z 
