DARWIN ON EVOLUTION 273 



the limits of variation, but did not believe that 

 the limits were necessarily permanent. He held 

 that the appearance of variations was an indirect 

 response to the conditions of life, their character 

 being determined by internal causes and not by 

 the nature of the external stimulus. 



It is generally assumed that Darwin did not 

 consider the question of the hereditary trans- 

 mission of acquired characters. Professor Meldola 

 has, however, pointed out to me the following 

 interesting passage which has appeared, with only 

 the sUghtest verbal change, in all editions of the 



'Some authors use the term "variation" in a technical 

 sense, as implying a modification directly due to the 

 physical conditions of life ; and " variations " in this sense 

 are supposed not to be inherited : but who can say that 

 the dwarfed condition of shells in the brackish waters of 

 the Baltic, or dwarfed plants on Alpine summits, or the 

 thicker fur of an animal from far northwards, would not in 

 some cases be inherited for at least some few generations ? 

 and in this case I. presume that the form would be called 

 a variety ' (1st Ed., 44, 45). 



Mr. Francis Darwin can throw no light upon 

 the ' authors ' referred to. It is deeply interesting 

 to observe that Darwin did not, even in 1844, 

 believe in the inheritance of the effects of 

 mutilation or of mechanical pressure.^ 



Francis Galton investigated the hereditary 

 transmission of individual differences and proved 



1 The Foundations of the Origin of Species, Cambridge (1909), 

 60-1. 



1 



