FLUCTUATIONS AND MUTATIONS 99 



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 Coelentera, where, as in plants, the contrast between germ- 

 plasm and somatoplasm has not been accentuated, as it is in 

 higher animals. It is quite conceivable 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 

 the more cautiously. An authority on domesticated animals. 

 Prof. Keller of Ziirich, finds but little evidence of it in the history 

 of the well-known stocks. 



It seems to us that in emphasising the importance of mutations 

 De Vries has swung to the extreme of greatly depreciating the 

 importance of fluctuations. Until we know more about animal 

 mutations, it does not seem to us legitimate to deny that fluc- 

 tuations may form, as Darwin believed, an important part of 

 the raw material on which selection operates. 



We cannot but regard with suspicion the distinction between 

 large fluctuations and small mutations. It seems to us a verbal 

 distinction. 



Finally, it must be remembered that, as De Vries frankly 



