PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 359* 



MUTATIONS 



While the evolution theory itself has been evolving, there has- 

 also been a great change of view concerning variations. Darwin 

 emphasized minute variations, — infinitesimal variations ; but 

 it is also true that he held that sudden conspicuous variations or 

 sports might occasionally lead to the origin of new varieties or 

 species. Bateson, in 1894. collected a vast number of such sud- 

 den variations ; but it was left for de Vries in his "Mutation 

 Theory" (We trespass on the botanists' domain!) to bring this- 

 matter to a position of importance in the thought of botanists- 

 and zoologists alike. De Vries distinguishes sharply between, 

 "fluctuations" and "mutations". The mutations of de Vries are 

 not necessarily of such extent as the "sports" of Darwin and 

 Bateson; but they are characterized l)y their infrequency, sud- 

 denness, and completeness, as contrasted with the freqvient and: 

 gradual fluctuations, — in other words, mutations are discon- 

 tinuous, fluctuations continuous. According to de Vries only 

 mutations are inheritaljle ; therefore only mutations can have 

 evolutionary significance, and this because mutations are due tO' 

 germinal variation, fluctuations to somatic modification. To 

 this extent, then, the mutations of de Vries are like the congenital 

 variations of Weismann, fluctuations comparable with acquired 

 characters ; but the enormous number of minute variations upon 

 which Weismann builds his theory of adaptive evolution would 

 hardly be accepted by de A'ries as mutations. 



The theory of de Vries is frequently quoted as annulling 

 the Darwinian theory of natural selection, — an utterly illegit- 

 imate statement of the over-zealous friends of mutation. Let 

 us hear de Vries himself: — "Darwin discovered the great prin- 

 ciple which rules the evolution of organisms. It is the principle 

 of natural selection. It is the sifting out of all organisms of 

 minor worth through the struggle for life. It is only a sieve, 

 and not a force of nature, no direct cause of improvement 

 as many of Darwin's adversaries, and unfortunately many of 

 his followers also, have so often asserted. It is only a sieve, 

 which decides which is to live and what to die. But evolutionary 



