92 MODERN IDEAS OF EVOLUTION 



to undergo a similar development under entirely 

 different conditions. It is scarcely too much to say 

 that these preposterous demands are usually made, 

 and tacitly assumed to be granted, in most dis 

 cussions as to the development of living beings in 

 geological time. 



But even if we were to grant these postulates, it 

 would be extremely difficult to fit the actual geo 

 logical succession into the mould thus arbitrarily 

 prepared for it ; and this we may perhaps be able to 

 illustrate by a few general statements and examples, 

 though its full elucidation would require an extended 

 treatise. 1 We shall, however, be able to see how far 

 this argument falls short of the force of demon 

 stration which has been claimed for it, and shall find 

 some grounds for the doubt with which it has been 

 viewed by many able palaeontologists. The com 

 plexity of the problems involved has indeed induced 

 many of those most familiar with the succession of 

 life to hold that, while we do not fully know its laws, 

 those that we do comprehend induce the belief that 

 they imply something very different from a continuous 

 and spontaneous evolution. The general truths that 

 we know on this great and complicated subject may 

 be shortly summed up as follows : 



I. Life originated very long ago. If in the Lau- 

 [rentian, or even in the early Cambrian, we can be sure 



1 See Story of the Earth and Chain of Life, by the Author. 



