18 Journal of the Mitchell Society [July 



are produced, not as Darwin thonglit by the gradual accumu- 

 lation of minute differences, but all at once bv the sudden ap- 

 pearance of full Hedged new characters which sharply dis- 

 tingiiish them from the parent species. 



The theory certainly leaped into favor. It cflFectively 

 disposes of the criticisms of Darwin's theory to which I have 

 referred. Furthermore, mutations instead of being extreme- 

 ly rare phenomena are almost becoming common. This is due 

 it would seem to the fact that mutationists are coming to lay 

 less emphasis upon the magnitude of a mutation and more 

 upon its heritability. Many of the departures that now pass 

 as mutations could I think very well be included under Dar- 

 win's variations. To claim heritability as a criterion between 

 mutations and Darwinian variations as seems now to be the 

 tendency would, in my judgment, rob Darwinism of all claim 

 that it has to bring an explanation of evolution, since it 

 leaves it in the absurd position of being based on non-heritable 

 variations. 



CEITICISM OF MUTATIOX 



For some years now there has l)een a growing suspicion 

 that the phenomena of mutation are really due to hybridi- 

 zation. The English geneticist, Bateson, seems to have been 

 first to suggest that Lamarck's evening primrose, upon which 

 De Vries primarily based his theory, is in reality a hybrid. 

 Much evidence has now accumulated to sustain this view. 



Davis, Professor of Botany at Pennsylvania, has attempt- 

 ed l)v hybridization to produce a complex type which in re- 

 production will behave like Oenothera Lamarckiana. He has 

 apparently succeeded in producing fairly constant hybrid 

 races which occasionally throw off mutants much as does the 

 classic example. Similar results have likewise been obtained 

 by Tower working with potato beetles. 



But in my judgment the most significant attack upon mu- 

 tation has been made by Jeffrey, of the Harvard Botanical 

 laboratory. Jeffrey investigated the evening primroses with 

 a view to determining the amount of sterility present. It 

 has long been known that infertility was characteristic of 



