No.. 304] 



THE FIXATION OF CHABAi TEE 



719 



explanation for their existence. This task must ultimately 

 be left to the sciences of physiology and genetics, and in 

 the meantime it is possible only to make suggestions and 

 conjectures as to what are the causes which underlie the 

 facts of conservatism. 



The very difficulties in the way of the explanation of 

 fixity proposed by the theory of natural selection suggest 

 a possible solution of one of the most conspicuous prob- 

 lems — why it is that just those characters of least physio- 

 logical importance and survival value are most con- 

 servative. May it not be true that the tendency toward 

 progressively increasing fixity, which seems to be almost 

 universal in organic evolution, has succeeded in render- 

 ing comparatively invariable those features which are of 

 little significance for survival, but that in the case of 

 vitally important characters this tendency has been over- 

 come by the opposing action of natural selection in elimi- 

 nating individuals which are not sufficiently plastic and 

 adaptable, and in thus maintaining or increasing the 

 variability of all characters important in the struggle for 



If this conception of the matter is a true one, the func- 

 tion of natural selection is almost precisely the reverse of 

 what it is ordinarily supposed to be, for instead of operat- 

 ing to fix characters and preserve types intact its action 

 results in their elimination, in so far as they interfere 

 with success, and in the placing of a premium on versa- 

 tility. Selection, in other words, is made for general 

 adaptability under varying conditions rather than for the 



