No. 537] INHERITANCE OF THE "EYE" IN VIGNA 519 



a slightly different group of atoms for a single side 

 chain in a molecule of chromatin or one of the constit- 

 uents of chromatin, or any one of numerous other 

 changes, might determine whether pigment is to be 

 formed in a given cell, or whether it may be produced at 

 all. But if the change which is responsible for the dif- 

 ference between two related organisms is a change in 

 any permanent organ of the cell, then the difference in 

 question will be hereditary. If it occurs in the material 

 of a chromosome, or any other cell organ that behaves 

 as a chromosome does in the reduction division, the dif- 

 ference in question will Mendelize. 



Let us suppose, merely for purposes of illustration, 

 that the difference between fully pigmented seed coat and 

 the Holstein coat pattern is due to a difference in the 

 rate at which a particular chromosome manufactures 

 a particular enzyme under given conditions. Then when 

 these two patterns are crossed we should get the usual 

 phenomena of monohybridism, with the ratio 3:1 (or 

 1:2:1). Thus the IToMein pattern is not necessarily 

 due to the "loss" of a "factor"; it may be due to some 

 such cause as a difference in the quantity of an enzyme 

 produced by a particular chromosome. The use of such 

 expressions as "presence of a factor" and "absence of 

 a factor" in what follows is therefore not meant to 

 imply the presence of a morphological entity in one race 

 and its absence in another. It rather means that in one 

 race some cell organ, probably a chromosome in Men- 

 delian inheritance, performs a certain function differ- 

 ently, or under different conditions, in the two races. 

 Since the phenomena of Mendelian inheritance point 

 clearly to the physical behavior of some cell organ, I 

 prefer to think of the symbols used in expressing the 

 genetic constitution of a type as representing the bodies, 

 differences in the functions of which give rise to the 

 character "pair." 



Thus the symbol W in what follows may be considered 

 as representing a cell organ which, under certain con- 

 ditions, performs a certain function in such a way as to 

 account for the difference between Small Eye and Wat- 



