XI ] EVOLUTION IN BIOLOGY. 305 



explain such cases deductively from the doctrine of 

 evolution than endeavour to support the doctrine of 

 evolution by them. For it is almost impossible to 

 prove that any structure, however rudimentary, is 

 useless that is to say, that it plays no part whatever 

 in the economy ; and, if it is in the slightest degree 

 useful, there is no reason why, on the hypothesis of 

 direct creation, it should not have been created. 

 Nevertheless, double-edged as is the argument from 

 rudimentary organs, there is probably none which 

 has produced a greater effect in promoting the general 

 acceptance of the theory of evolution. 



6. The older advocates of evolution sought for 

 the causes of the process exclusively in the influence 

 of varying conditions, such as climate and station, or 

 hybridisation, upon living forms. Even Treviranus 

 has got no farther than this point. Lamarck intro- 

 duced the conception of the action of an animal on 

 itself as a factor in producing modification. Starting 

 from the well-known fact that the habitual use of a 

 limb tends to develop the muscles of the limb, and to 

 produce a greater and greater facility in using it, he 

 made the general assumption that the effort of an 

 animal to exert an organ in a given direction tends to 

 develop the organ in that direction. But a little 

 consideration showed that, though Lamarck had seized 

 what, as far as it goes, is a true cause of modification, 

 it is a cause the actual effects of which are wholly 

 inadequate to account for any considerable modifica- 

 tion in animals, and which can have no influence at 

 all in the vegetable world ; and probably nothing con- 



