768 THE AMERICAN NATURALIST. [Vol. XXXVII. 



the principal evidence furnished by plants was made by Kors- 

 chinsky in 1 899. Systematic observations upon the subject were 

 begun by deVries in 1886 and have been continued until the 

 present time. As a result of his investigations deVries formu- 

 lated his "Mutationstheorie," which has appeared in book form, 

 the separate parts of which have been published in the period of 

 1 90 1 - 1 903 . This hypothesis rests upon the theory of pangenesis 

 previously formulated by him. 



The parent type, O. lamarckimia, from which deVries saw 

 mutant forms arise has been found constant in its characters in 

 cultivation in Europe and America and also when running wild. 

 This type is not identical with any known member of the Ameri- 

 can flora, and is most nearly allied to Onagra biennis grandiflora 

 {Oenothera biennis grandiflora) from which it is suggested it 

 might have arisen by mutation. 



The mutant derivatives of the parent form are found to be 

 constant in their characters, with no connecting or intergrading 

 forms, as illustrated by the cultures of the parent, (E. nanella 

 and (E. rubrinervis, in the New York Botanical Garden during 

 1 902- 1 903. The mutants are clearly separable from the parent 

 and from each other both by physiological and taxonomic stand- 

 ards. Furthermore the specific character of the mutants was 

 borne out by their behavior when hybridized with one another. 



It has become evident from the results so far accomplished 

 that the testing, study, proof or disproof of the theory of the 

 origin of species by mutation involves an actual examination of 

 hnes of descent, and observations upon successive generations 

 of organisms of known genesis. In this manner only may 

 mutant forms be distinguished from hybrids, individuals with 

 aberrant non-transmissible characters and teratological formations. 

 The nature of the questions involved, and the essentially mate- 

 rial character of the evidence to be considered is such that all 

 controversial discussions not supported by facts of this character 

 must be viewed with distrust. In no instance is this more 

 plainly apparent than in the recent treatment of the subject by 

 Vernon (Vernon, H. M. Variation in Animals and Plants. 1903). 

 This author says "Hence it {CEnothem lamarekiana) is probably 

 a garden variety of CEnothein biennis (Evening Primrose), and 



