PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE 119 



many interesting relationships may occur between the fac- 

 tors governing the production of characters. For example 

 it has been found that two or more determiners are often 

 present, either of which will produce the given character, as 

 Nillson-Ehle demonstrated in hybrids of brown and white 

 chaffed wheat, while on the other hand two or more deter- 

 miners acting together may be necessary to bring about an 

 effect. Such a condition exists as Bateson in 1910 showed 

 in certain white flowered sweet peas which when crossed 

 produce purple flowers in the first hybrid generation. The 

 results which have led to the theory of coupling and of 

 repulsion, particularly the latter where the expectancy of a 

 pure recessive may be one among many thousands, go far 

 toward suggesting a possible explanation of many so-called 

 mutations on the basis of ancestral individuals heterozyg- 

 ous for one or more characters. 



Do the Mendelian principles assist us, however, in at- 

 taining the goal which we are seeking, namely, the building 

 up of an ideal organism which will continue to transmit its 

 characters. The answer must be in the negative so far as 

 the originating of anything new is actually concerned. Re- 

 cessives may be obtained. Characters may be redistributed. 

 They were present in the forms first utilized, however. 



The Mutation Theory formulated by Devries in 1901 

 approximately at the time interest was being awakened by 

 the rediscovery of the hybridization principles of Mendel 

 needs no extended explanation to those who have been 

 interested in evolution. Based on cultural experiments with 

 Oenothera lamarckiana, one of the evening primroses, the 

 appearance of relatively small numbers of forms which 

 were quite distinct from the parental species and which 

 bred true in subsequent generations led to the inference that 

 evolution had in many cases proceeded by discontinuous 

 variations or mutations. 



Long series of breeding experiments followed in con- 

 nection with other organisms, both plants and animals, with 

 results quite similar to those obtained by DeVries. Investi- 



