1^6 Arend. L. Hagedoorn and A. C. Hagedoorn. 



F makes no difference by its presence or absence, unless E be 

 also present, when the grain will be darker coloured, and the flower 

 purple. Grains of this colour stick rarely all together in a pod. 



Finally there is G, which is present in plants with broad pods, 

 and not in those with narrow pods. There is a decided difference, 

 in respect to coherence of the seed, between plants with, and those 

 without this gene. 



This case beautifully illustrates that the difference between Poly- 

 vieres and other Genes is only caused by the amount of our knowledge 

 of the genes involved. When we hardly know them, and only, that 

 they have, among possible other qualities, also each about the same 

 influence on a certain character, we may call them Polymeres, but 

 as soon as we get to know more about them, or more surely still, in 

 those cases, in which we already know such genes in their influence 

 on other points, we will not call them by that name. 



It has, of course, never been the intention of Prof. Lang to 

 express the idea that polymeres differ in a fundamental way from 

 other genes. He simply happens to look at genes from the point of 

 the characters they influence, and not reversely. And because he 

 tends to study characters, rather than genes, he naturally wants to 

 class the genes with an eye to their relation to characters. Thus, it 

 is from his point of view, sufficiently remarkable, that groups of 

 genes all influence the same quality in the same direction. There is 

 nothing to be said against this view. 



The danger only arises from the fact, that it is all too easy to 

 think, that such groups of genes all influence such a character in the 

 same way, speaking physiologically, and that they must therefore be 

 fundamentally of the same nature, for instance chemically, which 

 assumption is manifestly unwarranted by the facts we find in the 

 better-studied cases. 



Lang will never make this mistake, but others will. We have 

 already read about "characters which are determined by one, and 

 others by several determinants" and "characters having a multiple 

 representation in the germ", all unavoidable consequences of the 

 polymere-idea on the unit-character-way of thinking. 



The distinction between Polymeres and other genes ought to be 

 abandoned by all those, who want to get rid of the term "unit- 

 character". 



In writing the genetic formulae it is better to use different signs 

 for all genes, instead of using the same letter, a\ a^, a^ etc., for 



