LAMARCK 



other swimming birds; others wade and by the effort 

 to escape from the mud stretch their legs, these grow 

 long and the birds become long-legged waders; others 

 stretch their necks and so develop long necks and 

 bills. 



His best known example is probably the explana- 

 tion of the neck of the giraffe. "This animal, the 

 largest of the mammals, inhabits the interior of Afri- 

 ca and, as it frequents places where the regions are 

 nearly always arid and without grass, it is compelled 

 to browse on the leaves of trees and is forced to reach 

 upwards continually. This habit, indulged in for a 

 long time by all the individuals of the race, has re- 

 sulted in lengthening the fore-legs more than the 

 hind-legs, and has so elongated the neck that the 

 giraffe, without rising on its hind-legs, elevates its 

 head and reaches upwards six metres, or almost twen- 

 ty feet."'' 



These are typical examples of Lamarck's reasoning 

 and will be used later when this theory is compared 

 with that of natural selection. 



The belief that use increases and modifies a muscle 

 or an organ by stimulating its nervous and blood sup- 

 ply, and that disuse causes it to become atrophied, 

 is pretty generally accepted; the only question is 

 whether such variations, occurring during the life of 

 the individual which has acquired the variation, are 

 transmitted to its offspring or whether variations 



'^'^ Ibid., vol. I, pp. 240-65 [pp.1 15-27]. 



C 181 2 



