488 



OEiaiN AND DISTRIBUTION OF MAN. 



[Ch. XLIII. 



difficult for him to derive from tliem 



successive steps made 



in an ascensive scale^ if, as some 



physiologists suspect, tlie quality of tlie brain has often 



moi 



But althougli size alone may be no safe criterion of relative 



ment 



individuals of transcendent ability would exceed in their 



dimens 



of inferior mental power. 



Whether the brain, like any 



matters 



some 



other organ, gains strength by exercise, and whether an 

 improvement thus acquired in the intellectual faculties may 

 be handed down to the offspring by inheritance, are still 



But no one is disposed to dispute 



_ m, or instinct, be pro- 

 duced by what is called ' spontaneous variation,' there is a 

 decided propensity in the new structure or attribute to 

 perpetuate itself by inheritance, as in the case of the six- 

 fingered variety of man, before mentioned (p. 476), or the 

 stunted legs of the Ancon sheep (p. 312). 



If, therefore, it be part of the plan of nature that living 

 beings should occasionally give birth to varieties in some 

 slight degree more perfect in the specialisation of their parts 

 and organs, or in the perfection of an organ, instinct, or 



mental facultv. thnn hnd hn^n pninvprl h^r c^r r^f +1-,^^,'-^ ^^..^.i^ 



Natural 



Mr 



such individuals in the struggle for life. When 

 says that he does not believe in a law of necessary develop- 

 ment, he means that simple and unimproved structures may 

 sometimes be best fitted for simple conditions of life, and that 

 even a degradation instead of an advance in structure may 

 occasionally be advantageous. Nevertheless, in the long run, 

 there will be a tendency, in the higher and more perfect 

 organisms, to survive and multiply, not at the expense of the 



come 



tion, but at the expense of those which are most nearly allied to 

 them. The repeated failure of particular varieties having 



r 



_ ms and attributes somewhat superior to any of their pro- 

 genitors, by no means implies that the final predominance of 



_ 'H ■ 



such organisms is left to chance. It suffices that there should 



I 



