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IX. On the Impregnation of the Ovum in the Amphibia. (First Series.) 

 By GEORGE NEWPORT, F.R.S., F.L.S. fyc. 



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 rny observations on the 

 Amphibia, reserving to a future early occasion the continuation of those on the Inver- 

 tebrata 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 



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