No. 531] GENOTYPE CONCEPTION OF HEREDITY 147 



that Woltereck's view has been influenced by Wesenberg 

 Lund in this matter; but what might be fairly excused in 

 the latter is not allowable for an experimenter pretending 

 to work with cardinal questions of genetics. 



Discontinuity and constant differences between the 

 "genes" are the quotidian bread of Mendelism, and here 

 the harmony of Mendelism and pure line work is perfect. 

 We have dealt with some recent criticism of the pure line 

 results ; now it is time to look at Mendelism. The aston- 

 ishing evolution of this mode of research has given an 

 almost interminable stock of special results, and ca>es 

 that at first might seem incompatible with the Mendel- 

 ian views have been analyzed more thoroughly »»n a 

 large scale and have shown themselves quite in accord- 

 ance with Mendelism. The magnificent book of Bateson 

 gives a full account of this prosperous state of Mendel- 

 ian research. And it may be evident that Mendelism 

 gives the most striking verification of the essential point 

 in Galton's "stirp-hypothesis": the inadequacy of 

 the personal quality in heredity. At the same time it 

 overthrows totally the idea of "organs" as being repre- 

 sented by the unities of the "stirp," pointing out that 

 the personal qualities of the organism in t<>f<> are the re- 

 sults of the reactions of the genotypical constitution. 

 The segregation of one sort of "gene" may have influ- 

 ence upon the whole organization. Hence the talk of 

 "genes for any particular character" ought to be 

 omitted, even in cases where no danger of confusion 

 seems to exist. So, as to the classical cases of peas, it is 

 not correct to speak of the gene — or genes — for "yellow" 

 in the cotyledons or for their "wrinkles," — yellow color 

 and wrinkled shape being only reactions of factors that 

 may have many other effects in the pea-plants. It 

 should be a principle of Mendelian workers to minimize 

 the number of different genes as much as possible. 



Here we meet with the questions of correlation and 

 "coupling" of genes. I can not here enter into a discus- 

 sion as to the notion of "correlation" with its several 

 meanings; in my "Elemente der exakten Erblichkeits- 



