TNBIRECT EQUILIBRATION. 455 



fast does the production of specialities of character by 

 natural selection alone, become difficult. Particularly does 

 this seem to be so with a species so multitudinous in its 

 powers as mankind ; and above all does it seem to be 

 so with such of the human powers as have but minor shares 

 in aiding the struggle for life the aesthetic faculties, for 

 example. 



It by no means follows, however, that in cases of this kind, 

 and cases of the preceding kind, natural selection plays no 

 part. Wherever it is not the chief agent in working organic 

 changes, it is still, very generally, a secondary agent. The 

 survival of the fittest must nearly always further the produc- 

 tion of modifications which produce fitness ; whether they be 

 modifications that have arisen incidentally, or modifications 

 that have been caused by direct adaptation. Evidently, those 

 individuals whose constitutions or circumstances have facili- 

 tated the production in them of any structural change con- 

 sequent on any functional change demanded by some new 

 external condition, will be the individuals most likely to live 

 and to leave descendants. There must be a natural selection 

 of functionally-acquired peculiarities, as well as of incidental 

 peculiarities ; and hence such structural changes in a species 

 as result from changes of habit necessitated by changed cir- 

 cumstances, natural selection will render more rapid than 

 they would otherwise be. 



There are, however, some modifications in the sizes and 

 forms of parts, which cannot have been aided by natural 

 selection; but which must have resulted wholly from the 

 inheritance of functionally-produced alterations. The dwind- 

 ling away of organs of which the undue sizes entail no 

 appreciable evils, furnishes the best evidence of this. Take, 

 for an example, that diminution of the jaws and teeth which 

 characterizes the civilized races, as contrasted with the 

 savage races.* How can the civilized races have been bene- 



* I am indebted to Mr Flower for the opportunity of examining the collection 

 of ekulls in the Museum of the College of Surgeons for verification of this. Uu- 



