196 



THE AMERICAN NATURALIST [Vol. XL VI 



Critical analysis during the past two years by Davis 

 and by Gates 13 of the very species Oenothera Lamarck- 

 iana on which De Vries chiefly based his monumental 

 work, tends to show that 0. Lamarckiana is possibly a 

 hybrid of 0. biennis an&O. grandi flora and not a natural 

 species. Thus the " elementary species" which are 

 springing from it in various gardens may prove to be 

 comparable to the familiar results of hybridization in 

 mammals and birds. 



Davis, on the basis of his prolonged experimental 

 researches, says: 



Indeed, the theory of De Vries may fairly be said to rest chiefly 

 upon the behavior of this interesting plant, the account of which forms 

 so large a part of his work " Die Mutationstheorie " (2 vols., Leipzig, 

 (1901). ... In a brief perusal of the work one is struck by the opti- 

 mism of its author and the brilliancy and breadth of his exposition of 

 the views set forth. . . . The analysis of the data amassed by Darwin, 

 in which it is shown that Darwin's " single variations " are the same as 

 De Vries's mutations seems to the reviewer particularly effective. . . . 

 Probably the time will soon come when nearly all biologists will be 

 ready to admit that mutation or the sudden appearance of new forms 

 has been an important factor at least in species formation of plants 

 and animals. Admitting this it remains to be discovered what rela- 

 tion these sudden appearances bear to lln ejenend I rends of evolution 

 which are apparent in so man)/ phi/hujcnies [italics our own] . . . 

 for granting the facts of mutation we have only accounted for a micro- 

 ev>hin..n, and it 1- -til! m he -h.»v. n that l he larger tendencies can be 



of other factors. . . . 



The skepticism of both these botanists is striking. 

 Their opinions as to the existence of larger evolutionary 

 trends are exactly in accord with those of paleontologists. 



4. Evidence for Discontinuity from Mendelian Heredity 

 and Experimental Selection 

 The newest bulwark of the discontinuity hypothesis 

 is that erected since 1903 by the revival of the great dis- 



M Davis, Bradley Moore, "Genetieal Studies on (Enothera. II. Some 

 Hybrids of (Enothera biennis and O. gremdiflora that resemble O. Lamarck- 

 iana," Amer. Naturalist, Vol. XLV, April, 1913, pp. 193-233. Gates, 

 R. R., "Mutation in Oenothera," Amer. Naturalist. Vol. XLV, No. 538, 

 October, 1911, pp. 577-606. 



