MUTATION 163 



a new kind of molecule, the appearance of red 

 pigment where none was, are all qualitative 

 changes. Weismann's admission that red gran- 

 ules may arise de novo in consequence of a molec- 

 ular change in the germ-plasm is an admission 

 that an organism may undergo a quahtative va- 

 riation, and this is a mutation. Recalling, then, 

 in recapitulation, that every character of an or- 

 ganism has a chemical basis, that a new character 

 implies one or more new kinds of molecules and 

 that molecular change is essentially qualitative 

 and discontinuous, the conclusion seems safe that 

 variations involving new characters are essen- 

 tially discontinuous, and consequently of the 

 order of mutations. 



DARWINIAN VARIATIONS 



At this time the Weismannian view and that 

 of the neo-Darwinists in general is of less interest 

 than that of Darwin himself. What was Dar- 

 win's attitude on the question whether variations 

 that play a part in evolution are of the qualita- 

 tive or the quantitative order? The answer 

 seems to be simple; the question did not present 

 itself to him — our formulation of the matter is 

 a comparatively recent product of scientific anal- 

 ysis. Darwin did recognize saltation as opposed 

 to ordinary variability, and remarks : " It is dif- 

 ficult to drawn any distinct hne between a vari- 

 ation and a monstrosity." In his Variation of 

 Animals and Plants under Domestication, Dar- 



