702 Mutations 



thera brevistylis. Most of the others quickly 

 disappear. 



This failure of a large part of the productions 

 of nature deserves to be considered at some 

 length. It may be elevated to a principle, and 

 may be made use of to explain many diffi- 

 cult points of the theory of descent. If, in 

 order to secure one good novelty, nature must 

 produce ten or twenty or perhaps more bad 

 ones at the same time, the possibility of im- 

 provements coming by pure chance must be 

 granted at once. All hypotheses concerning the 

 direct causes of adaptation at once become su- 

 perfluous, and the great principle enunciated by 

 Darwin once more reigns supreme. 



In this way too, the mutation-period of the 

 evening-primrose is to be considered as a proto- 

 type. Assuming it as such provisionally, it may 

 aid us in arranging the facts of descent so as to 

 allow of a deeper insight and a closer scrutiny. 

 All swarms of elementary species are the re- 

 mains of far larger initial groups. All species 

 containing only a few subspecies may be sup- 

 posed to have thrown off at the outset far more 

 numerous lateral branches, out of which how- 

 ever, the greater part have been lost, being 

 unfit for the surrounding conditions. It is 

 the principle of the struggle for life between ele- 

 mentary species, followed by the survival of the 



