SIMULA TION BY NA TURAL SELECTION. 83 



monkeys, or the displaced eyes of soles, or the 

 altered number of teeth in plaice, or the increased 

 fertility of domesticated animals, or the shortened 

 legs and snouts of pigs, or the shortened intestines 

 of tame rabbits, or the lengthened intestines of 

 domestic cats, &C. 1 Changed habits and the requi- 

 site change of structure will usually be favoured 

 by natural selection ; for habit, as Darwin says, 

 " almost implies that some benefit great or 

 small is thus derived." 



SIMILAR EFFECTS OF NATURAL SELECTION AND 

 USE-INHERITANCE. 



Here we perceive a difficulty which will equally 

 trouble those who affirm use-inheritance and those 



1 Origin of Species, pp. 188, no; Descent of Man, pp. 32 35 ; 

 Variation of Animals and Plants under Domestication, ii. 289, 

 293. Use or disuse during lifetime of course co-operates, and in 

 some cases, as in that of the canoe Indians, may be the principal 

 or even perhaps the sole cause of the change. 



G 2 



