EVOLUTION AS A NATURAL PROCESS 133 



its immediate purpose of giving a natural explanation 

 of how evolution may be partly accounted for. 



Before proceeding to the post-Darwinian investiga- 

 tions that have done so much to amplify the account 

 of natural evolution, let us consider the contrasted 

 explanation given by Lamarck and his followers. As 

 we have stated earlier, Lamarckianism is the name given 

 to the doctrine that modifications other than those due 

 to congenital factors may enter into the heritage of 

 a species, and may add themselves to those already 

 combined as the peculiar characteristics of a particular 

 species. Let us take the giraffe and its long neck 

 as a concrete example. The great length of this 

 part is obviously an adaptive character, enabling the 

 animal to browse upon the softer leafy shoots of shrubs 

 and trees. The vertebral column of the neck comprises 

 just the same number of bones that are present in the 

 short-necked relatives of this form, so that we are 

 justified in accepting as a fact the evolution of the 

 giraffe's long neck by the lengthening of each one of 

 originally shorter vertebrae. The Lamarckian explana- 

 tion of this fact would be that the earliest forms in 

 the ancestry of the giraffe as such stretched their necks 

 as they fed, and that this peculiar function with its 

 correlated structural modification became habitual. 

 The slight increase brought about by any single in- 

 dividual would be inherited and transmitted to the 

 giraffes of the next generation ; in other words, an 

 individually acquired character would be inherited. 

 The young giraffes of this next generation would 



