ORIGIN OF LOWEST ORGANISMS. 



similar to those by which crystals arise. To rely 

 too exclusively upon an argument from analogy is 

 always perilous : it is more than usually so, how- 

 ever, in a case like this, where what is practically 

 an opposing analogy may be deemed to speak just 

 as authoritatively in an opposite direction. 



There is one consideration, moreover, which deserves 

 to be pointed out here, and which does not seem to 

 have occurred to most of those who so firmly pin their 

 faith to the truth of the motto " omne vivum ex vivo'' 

 The every-day experience of mankind, supplemented 

 by the ordinary observations of skilled naturalists, does 

 pretty fairly entitle us to arrive at a wide generaliza- 

 tion, to the effect that some representatives of every 

 kind of organism are capable of reproducing similar 

 organisms. But, whilst this is all that the actual 

 every-day experience of mankind warrants being said, 

 and whilst there is in reality the widest possible gulf 

 between such a generalization and that which is ex- 

 pressed by the motto " omne vivum ex vivo" the 

 latter formula has of late been spoken of as though 

 it were the one which was in accordance with the daily 

 experience of mankind, rather than the other, which 

 gives expression to a generalization of a much nar- 

 rower description. This experience, in reality, affords 

 no evidence which could entitle us to place implicit 

 belief in the formula " omne vivum ex vivo'' 



Whilst we do know something about the ability 

 which most organisms possess of reproducing similar 



