THE MUTATION THEORY 115 



same individual may be quite different. When with this pos- 

 sibility in view the behaviour of the types is re-examined I 

 anticipate that many of the difficulties will be removed. 



Outside the evidence from Oenothera, which, as we have seen, 

 is still ambiguous, I know no considerable body of facts favour- 

 able to that special view of Mutation which cfe Vries has pro- 

 mulgated. Of variation, or if we will, Mutation, in respect of 

 some one character, or resulting from recombination, there is 

 proof in abundance ; but of that simultaneous variation in several 

 independent respects to which de Vries especially attributes the 

 origin of new specific types I know only casual records which 

 have yet to undergo the process of criticism. 



Besides de Vries's " Mutationstheorie" and "Species and Vari- 

 eties" the chief publications relating to the subject of the be- 

 haviour of Oenothera are the following: (Many other papers 

 relating especially to the cytology of the forms have appeared.) 



Davis, B. M. Genetical Studies on Oenothera, I. Amer. Nat., XLIV, 1910, p. 108. 



Genetical Studies on Oenothera, II. Ibid., XLV, 1911, p. 193. 

 Gates, R. R. An Analytical Key to some of the Segregates of Oenothera. Twen- 

 tieth Annual Report of the Missouri Botanical Garden, 1909. 

 Studies on the Variability and Heritability of Pigmentation in Oenothera. 



Ztsch.f. Abstammungslehre, 1911, IV, p. 337. 



Honing, J. A. Die Doppelnatur der Oenothera Lamarckiana. Ztsch. f. Abstam- 

 mungslehre, 1911, IV, p. 227. 



Macdougal, D. T. (with A. M. Vail, G. H. Shull, and J. K. Small). Mutants and 

 Hybrids of the Oenotheras. Carnegie Institution's Publication, No. 24, 

 1905. 



Macdougal, D. T., Vail, A. M., Shull, J. H. Mutations, Variations and Relation- 

 ships of the Oenotheras. Carnegie Institution's Publication, No. 81, 1907. 

 de Vries, H. On Atavistic Variation in Oenothera cruciata. Bull. Torrey Club, 



1903. Vol. 30, p. 75- 



On Twin Hybrids, Bot. Gaz., Vol. 44, 1907, p. 401. 

 Ueber die Zwillingsbastarde von Oenothera nanella. Ber. Deut. Bot. Ges., 



1908, XXVI, a, p. 667. 



Bastarde von Oenothera gigas. Ibid., p. 754. 

 On Triple Hybrids. Bot. Gaz., 1909, Vol. 47, p. I. 

 Ueb. doppeltreziproke Bastarde von Oenothera biennis L. und Oenothera 



muricata L. Biol. Cbltt., 1911, XXXI, p. 97. 



Zeijlstra, H. H. Oenothera nanella de Vries, eine krankhafte Pflanzenart. Biol. 

 Cbltt., 1911, XXXI, p. 129. 



