The Mutation Hypothesis. 65 



elementary species or subspecies. Bateson expressly 

 points out that the law of elementary species holds good 

 for the animal as well as for the vegetable kingdom ; 

 but that these forms have as yet received much too little 

 attention. Elementary species are sharply and completely 

 separated from one another, they do not merge into one 

 another, either in the wild state, or under cultivation 

 (provided that crossing does not occur). 



This sharp delimitation of the elementary species is 

 so general a phenomenon that it certainly points to a dis- 

 continuous origin. The main object of Bateson's book 

 is to arrange and collect the material in such a way as 

 to give some insight into this discontinuity.^ 



A very serious objection to the theory of selection is 

 brought forward by him in reference to the usefulness of 

 specific characters." It has been repeatedly asserted by 

 Darwin and others that the characters which separate 

 allied species from one another are not of particular ad- 

 vantage in the struggle for existence, but are as a rule 

 useless and inconsiderable. Nevertheless these differ- 

 ences are often, apparently, very complex and constant 

 characters but "of doubtful value." The existence of 

 such characters cannot be accounted for by Wallace^s 

 theory of selection which explains useful characters in 

 so beautiful and simple a manner. The mutation theory, 

 on the other hand, gives a perfectly simple explanation 

 of the existence of such characters ; for useless, but not 

 dangerous, mutations must appear as often as useful ones, 

 and have almost as much likelihood as these of per- 

 sisting. 



^ Species are discontinuous ; may not the variation by which spe- 

 cies are produced, be discontinuous too? p. i8. See also pp. 69,568. 



^ Page II. 



