Chap. XXL] AND CONCLUDING REMARKS. 371 



future. In the greater number of cases, we can only say 

 that the cause of each slight variation and of each mon- 

 strosity lies much more in the nature or constitution of 

 the organism, than in the nature of the surrounding con- 

 ditions ; though new and changed conditions certainly 

 play an important part in exciting organic changes of all 

 kinds. 



Through the means just specified, aided perhaps by 

 others as yet undiscovered, man has been raised to his 

 present state. But since he attained to the rank of man- 

 hood, he has diverged into distinct races, or, as they may 

 be more appropriately called, subspecies. Some of these, 

 for instance, the Negro and European, are so distinct that, 

 if specimens had been brought to a naturalist without any 

 further information, they would undoubtedly have been 

 considered by him as good and true species. Neverthe- 

 less all the races agree in so many unimportant details of 

 structure and in so many mental peculiarities, that these 

 can be accounted for only through inheritance from a com- 

 mon progenitor ; and a progenitor thus characterized 

 would probably have deserved to rank as man. 



It must not be supposed that the divergence of each 

 race from the other races, and of all the races from a com- 

 mon stock, can be traced back, to any one pair of progeni- 

 tors. On the contrary, at every stage in the process of 

 modification, all the individuals which were in any way 

 best fitted for their conditions of life, though in different 

 degrees, would have survived in greater numbers than the 

 less well fitted. The process would have been like that 

 followed by man, when he does not intentionally select 

 particular individuals, but breeds from all the superior 

 and neglects all the inferior individuals. He thus slowly 

 but surely modifies his stock, and unconsciously forms a 

 new strain. So with respect to modifications, acquired 

 independently of selection, and due to variations arising 



