294 The Study of Animal Life PART iv 



of this doctrine on various groups of phenomena ; and (c) he 

 essayed the problem of the factors in evolution. 



(a) The man who makes us believe a fact is to us 

 more important than the original discoverer. And so 

 Darwin gets credit for inventing the theory of descent, 

 which in principle is as old as clear thought itself, and in 

 its biological application was stated a hundred years before 

 the publication of the Origin of Species (1859). The con- 

 ception was no new one, but Darwin first made men believe 

 it. The idea was not his, but he gave it to many. He did 

 not originate ; he established. He converted naturalists to 

 an evolutionary conception of the organic world. 



(b) Having got people to believe the theory of 

 descent, the theory of development out of preceding 

 conditions, Darwin went on to' show how the conception 

 would illumine all facts to which it was applicable. In his 

 work on the expression of emotions, and in scattered chap- 

 ters, he showed how the light might be shed upon the 

 secrets of mental activity. Whenever it was seen that 

 the doctrine could justify itself in regard to general organic 

 life, it was eagerly seized as an organon for the exploration 

 of special sets of facts. The phoenix revived and flew 

 croaking amid the smoke of burning systems. How one 

 discussed the evolution of language, and another that of 

 industry ; how the natural history of ethics was sketched 

 by one thinker, and the descent of institutions by another ; 

 how the conception has forced its way into the cloister 

 and the political arena, and has even found expression in 

 theories of literature, art, and religion, is an often-repeated 

 story. 



(c) We have noticed that Buffon, and, let us add, Trevir- 

 anus, firmly maintained that the direct influence of the 

 external conditions of life was an important factor in evolu- 

 tion. We have also seen that Erasmus Darwin and Lamarck 

 were strongly convinced of the transforming power of use 

 and disuse. When Charles Darwin began to think and 

 write on the origin of species, he also recognised the trans- 



forming influences of function and of environment. But 

 with the Buffonian or Lamarckian position he was never 



