98 HEREDITY AND VARIATION 



(4) Fluctuations do not yield anything really new, they imply a 

 little more or a little less of characters already present : mutations 

 are novelties, they imply some new pattern, some new position of 

 organic equilibrium. According to De Vries's theory, no new 

 species can be established without mutation. "When a muta- 

 tion has occurred a new species is already in existence, and will 

 remain in existence, unless all the progeny of the mutation are 

 destroyed." . . . The phrase " survival of the fittest," as de- 

 scribing a process of evolution, ought to be replaced by " survival 

 of the fittest species." According to De Vries, species originate 

 by mutation instead of by the continuous selection of fluctuations. 

 " Natural Selection may explain the survival of the fittest, but it 

 cannot explain the arrival of the fittest." 



In regard to these far-reaching conclusions it should be noted 

 that while De Vries has given much convincing evidence in regard 

 to plants, we have as yet very slight evidence of the origin of 

 species of animals by mutation. We know of many discontinuous 

 variations among animals, but the subsequent history of these is 

 not known except in a few cases. It must be remembered that, 

 morphologically regarded, the whole vegetable kingdom does not 

 correspond to more than the first three or four phyla in the animal 

 kingdom to the Protozoa, Porifera, and Ccelentera, where, as in 

 plants, the contrast between germ-plasm andsomatoplasm has not 

 been accentuated, as it is in higher animals. It is quite conceiv- 

 able that a mode of evolution common among plants may be rare 

 among animals. It is difficult at present to apply the mutation 

 concept with security to the animal kingdom. 



The idea of mutation is very welcome because it lessens the 

 burden which it has been found theoretically necessary to lay on 

 the shoulders of the selection hypothesis, and because it fits in well 

 with the a priori convictions which some naturalists have as to 

 the autonomy of the organism, that it is as much a self -changing 

 insurgent Proteus as a pawn in a game which the Environment 

 plays. But because it is so welcome, it is to be entertained 



