54 THE PROBLEMS OF EVOLUTION 



effects of use and disuse, and at one time expressed 

 the belief that the incidence of new conditions 

 over a succession of generations might result in 

 greater variation. He did not, of course, have the 

 knowledge necessary to an appreciation of the re- 

 combination of characters by sexual reproduction 

 which is now known to be so important, but even 

 so we find him writing: "A certain degree of varia- 

 tion seems inevitable effect of process of reproduc- 

 tion." 1" 



Other writers have taken various attitudes to- 

 ward the causes of variation. They could not fail 

 to recognize the occurrence of variations, even as 

 Darwin did, but recognition is not explanation 

 and the trend of modern science is inquiry into 

 causes to the utmost possible degree. In 1909 

 Bateson wrote: "In reply to the question so often 

 asked, Has modern investigation given evidence as 

 to the nature of these causes.^ the answer must still 

 be. Almost nothing." ^ In 1913 he inquired at 

 length into the causes of variation,^ but still found 

 no satisfactory explanation. His diflSculty in satis- 

 fying himself on the addition of characters to an 

 organism is a very real one, and if we concern our- 

 selves with specific causes we must admit that his 

 recognition of scientific ignorance is valid. The 



^'^See footnote 1, part a. 



2 Mendel's Principles of Heredity, p. 279, 1909. 



* Problems of Genetics, 1913. 



