160 NOTE ON ALTERNATION OF GENERATIONS, ETC. 



imbibition, and of propagation by spontaneous fission, 

 as those to which itself owed its origin. 



Owen maintains that this constitutes Partheno- 

 genesis. Some of the cells, instead of being trans- 

 formed into tissues, remain, unchanged as cells, in- 

 cluded in the body, where they repeat the original 

 process of sub-division, and produce offspring, as 

 they themselves were produced. Professor Owen also 

 states why this reproduction has its limits. The 

 original cell, by frequent sub-division, gradually loses 

 a portion of its plastic force. If at first starting it 

 had a force of 100, after passing through 50 sub- 

 divisions it is reduced to a force of 2. Thus Parthe- 

 nogenesis is not indefinitely prolonged. 



To many, Owen's theory appears as satisfactory as 

 it is ingenious, while others maintain that it leaves 

 the subject unexplained. It may be regarded, there- 

 fore, as still subjudice. 1 



1 Owen on Partheiingt-iusis , Lewes's Sfa-Side Studies. 



KDISBCRGH : T. CONSTABLE, PRINTER TO HER MAJESTY. 



