20 THE SURVIVAL OF THE UNLIKE. [l. 



convergent histories. Every naturalist, therefore, is 

 compelled to admit that differences in nature have some- 

 how been augmented in the long processes of time. It 

 is unnecessary, therefore, that he seek the causes of pres- 

 ent differences until he shall have determined the causes 

 of the smallest or original indifferences. It is thus seen 

 that there are two great and co-ordinate problems in the 

 study of evolution, — the causes of initial differences, 

 and the means by which differences are augmented. 

 These two problems are no doubt very often expressions 

 of the same force or jiower, for the augmentation of a 

 difference comes about by the origination of new degrees 

 of difference; that is, by new differences. It is very 

 probable that the original genesis of the difference is 

 often due to the operation of the very same physiological 

 processes which gradually enlarge the difference into a 

 gulf of wide separation. 



In approaching this question of the origin of unlike - 

 nesses, the inquirer hiust first divest himself of the effects 

 of all previous teaching and thinking. We have reason 

 to assume that all beings came from one original life- 

 plasma, and we must assume that this plasma had the 

 power of perpetuating its physiological identity. Most 

 persons still further assume that this plasma must have 

 been endowed with the property of reproducing all its 

 characters of form and habit exactly, but such assump- 

 tion is wholly gratuitous and is born of the age-long 

 habit of thinking that like produces like. We really 

 have no right to assume either that this plasma was or 

 was not constituted with the power of exact reproduction 

 of all its attributes, unless the behavior of its ascendents 

 forces us to the one or the other conclusion. Inasmuch 

 as no two individual organisms ever are or ever have 



