T/jA Arend. L. Hagedoorn and A. C. Hagedoorn. 



Nilsson-Ehle has studied a series of genes, which all, by their 

 cooperation to the development of a wheatplant, tend to make the 

 colour of its grain darker. How these factors exert this influence, 

 (speaking physiologically) we do not know at all, nor do we know, 

 what other characters of wheat each one of them may influence. It 

 is easy to see, that the two last cases are completely analogous. With 

 the exception, that we know more of the factors influencing eye-colour 

 of the mouse, than about those influencing grain-colour of wheat. 



Prof. Arnold Lang has used Nilsson-Ehles example to give a 

 tentative rational explanation of some cases of so-called blending 

 inheritance, notably of the fact that Castle obtained young rabbits, 

 intermediate between their parents in earlength, from which young 

 in a limited number of offspring, he obtained none with an earlength 

 as great as that of the grandmother, or as small as that of the grand- 

 father. He showed, that by assuming that several genes influenced 

 earlength, a very plausible explanation of this case could be given. 

 But he went further, he invented a new term to be applied in such 

 cases, Polymerie. To cite his own words: Von Polymerie könnten wir 

 also sprechen, wenn eine bestimmte Eigenschaft in den Gameten von 

 mehreren gleichartigen aber selbständigen Genen bedingt würde, deren 

 Wirkungen sich kumulieren. 



This wholly technical point is, we think, a weak spot in the 

 otherwisely admirable paper by Lang. For, what constitutes the 

 difference between Polymeres and other genes? Only this, that Poly- 

 meres would be "gleichartig", having the same nature. Now, do the 

 facts force us, to admit, that a number of Polymeres have more in 

 common than an equal number of other genes ? We mean, something 

 which should be of fundamental importance. 



Clearly, they have this in common, that they influence the deve- 

 lopment in the same direction. This is something. But would it not 

 be necessary to know that they influence the development in the same 

 way, to distinguish them from other genes? That two influences 

 have an analogous result does not necessarily stamp them as of one 

 kind. Far from it. If they had the same influence physiologically 

 it would be something different. If one genetic factor darkens the 

 colour of wheat by helping to produce in the grain a coloured sub- 

 stance, and a second genetic factor darkens the colour by making 

 the grain more transparent, what, we want to ask, have these two 

 things in common which justifies their being classed together? If 

 the factor h, which distinguishes richly coloured mice from fade ones. 



