THE TRANSMUTATION OF SPECIES. 259 



its neck. Now, the effect of such habitual efforts in 

 such a bird, and in all of its species, ought to be that 

 of producing in time a marked elongation of the neck; 

 and, as a matter of fact, such lengthening of the 

 neck is actually found in all shore-frequenting birds.' 



It will be evident from the above, as from the entire 

 tenor of his arguments upon this subject, that Lamarck 

 does not mean that a mere act of volition, apart from 

 any positive action, could effect any change in the 

 structure of an animal. He assuredly did not mean, 

 for example, to imply that the long legs of wading birds 

 were the result of the fact that repeated generations 

 of these birds had gone on wishing that their legs were 

 a little longer. All that his theory would imply in such 

 a case is, that when a change in the previous condition 

 of a region had driven certain formerly terrestrial birds 

 into the habit of wading in streams, pools, or the sea, 

 for the purpose of obtaining food, the necessity for 

 keeping their bodies dry had ultimately brought about 

 a lengthening of the bones of the leg, and a disappear- 

 ance of part of their covering of feathers. In other 

 words, Lamarck really means that the constant efforts 

 made by any and every animal to bring itself into accord 

 with its surroundings inevitably leads in course of time 

 to corresponding changes of structure. 



This point may be illustrated by an imaginary case. 

 As things stand at present, man has no necessity for 

 using his foot in prehension, his hand supplying all his 

 wants in this direction; and his great toe is therefore 

 practically useless as an organ of prehension. It is, 

 however, a well-known fact that men who leave the 



