96 THEORIES OF EVOLUTION 



in the organism, so that even if animals were brought up 

 alike, we know they would still be unlike, and so that, 

 however much the offspring may resemble their parents, 

 they are never exactly like their parents or exactly like 

 each other. There is, then, first, individual difference, 

 one of the most essential facts in the organism. 



Secondly, the fact of Heredity, — the fact that these 

 inherent differences may be and are inherited. Although 

 the hereditary transmission of acquired differences is 

 disputed, the transmission of those that are inherent 

 is certain. This stands before us as one of the most 

 obvious and certain of conclusions, equally proved by 

 the observation and experience of every one of us. 



Thirdly, the fact that there must be a Struggle for 

 Existence ; that there are far more individuals born into 

 the world in every species, even the most slowly increasing, 

 than can possibly survive and reproduce. 



These three factors must by logical necessity lead to 

 a survival of the fittest among individual variations. It 

 does not require a scientific mind to comprehend that, — 

 to infer that some amount of evolution must ensue from 

 the co-operation of those three factors, every one of which 

 stands firm and undisputed. Among all the advocates 

 of rival theories which have been brought forward to 

 explain evolution, no one has ever ventured to attempt 

 to disprove any one of these three factors. They stand 

 unchallenged. 



The politician, Henry Fawcett, saw, long before scien- 

 tific people themselves understood what Darwin meant 

 by Natural Selection, that logically some result must 

 ensue from such co-operation. Fawcett said that Natural 

 Selection must produce evolution as surely as a round 

 stone will roll further than a square one. Some measure 

 of evolution is simply the logical result of the co-opera- 

 tion of these three undisputed, abundantly proved factors. 



Now, certain writers have thought to undermine the 

 theory of Natural Selection by arguing that the important 

 and essential factor of individual variation is not explained 

 by the theory which rests upon it. True, it is not ; but 

 for the theory of Natural Selection, the explanation does 





