No. 602] MEN DELI AN FACTOR DIFFERENCES 97 



segregation in the gametic series of such forms. Beyond 

 this the CEnothera phenomena display a remarkably 

 orderly behavior, and, although complex in nature, such 

 orderliness points strongly to some kind of definite seg- 

 regation dependent upon the hereditary constitution of 

 the forms involved rather than upon any change in germi- 

 nal substance expressed in the gametic series. Lamarcki- 

 ana, for instance, produces constantly a small percentage 

 of nanella as well as a number of other forms. It is, 

 therefore, necessary to assume merely that nanella ga- 

 metes make up a small percentage of the gametic series in 

 LamarcJciana, When two nanella gametes meet, a nanella 

 individual is produced, and it breeds true, as might be ex- 

 pected. "When, however, a nanella gamete meets a La- 

 marckiana, gamete a Lamar ckiana individual is produced, 

 which need not necessarily differ in its behavior with re- 

 spect to the production of nanella from other Lamarcki- 

 ana races, since practically all of the combinations in- 

 volving nanella elements would fail to develop, or in case 

 some few of these combinations did develop, they might 

 produce other characteristic forms unlike either Lamarcki- 

 ana or nanella. This conception is in part borne out by 

 the fact that nanella appears to differ from Lamarcki- 

 ana not only in stature, but also in other characters, as is 

 shown in hybridization phenomena involving this form. 

 From this standpoint also, the occurrence of nanella in 

 the progeny of a wide range of forms is perfectly intel- 

 ligible. When nanella, which apparently really breeds 

 true, is crossed back with Lamarckiana a small propor- 

 tion of the progeny is of the nanella type and the rest are 

 Lamarckiana. This proportion is apparently greater 

 than that normally obtained from selfed Lamarckiana, 

 and this is merely a consequence of the realization of the 

 gametic ratio of nanellas in the Lamarckiana series as a 

 phenotypic ratio. The true breeding of the forms thus 

 resulting, to the extent that they breed true, is a natural 

 consequence of the germinal constitution of such forms. 

 On the other hand, when ruhrinervis, which never pro- 

 duces nanella as a "mutant" (Gates, 1915), is crossed 



