164 THE PROBLEMS OF EVOLUTION 



possibility of so-called acquired characters being 

 transmitted in some degree from generation to 

 generation. This remains the most conspicuous 

 controversial point, but it is certainly amenable 

 to laboratory investigation. 



Out of all of these facts we find that the muta- 

 tion theory has failed to establish one of its early 

 postulates, that new species arise suddenly by 

 saltation, just as the Lamarckian theory has failed 

 to establish the original laws of Lamarck. Indeed, 

 the available evidence is definitely contradictory 

 in both cases. Both views support the idea of 

 gradual change. Both recognize the close associa- 

 tion of environment and heritage in the establish- 

 ment of species. The difference between them 

 practically disappears save that they cling to the 

 ideas, respectively, of random variation acted upon 

 by selective forces and of a definite and direct 

 adjustment of the species through the lives of its 

 component individuals to the conditions of en- 

 vironment. 



The nearest that we can come to the actual proc- 

 ess of past evolution in nature is in the field of 

 palaeontology. The evidence is fragmentary. Only 

 here and there are series complete enough to yield 

 satisfying tales of long-continued change. But the 

 length of time covered by scientific observation of 

 living creatures is so short in proportion to the 

 periods obviously necessary for the consummation 



