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I. NAG AI : 
separable at the time of synapsis. Tlie character which is due to the end 
product of the final change, therefore would appear as due also to a single 
genetic entity. Supposing that the purple anthocyanin is produced by C-*R->P 
changes and three separate genes are actually taking part to bring about 
complex chemical changes. But if these genes are linked, or so to say, form 
a complex, and do not separate in gametogenesis, they may well be considered 
as a single entity and can be substituted by a single designation to express 
the genetic entities to a given character. When they separate from the complex 
by any cause, a supposed single unit character would appear to be constituted 
by more than a single gene. 
The separation of genes from the complex may take place either by 
hybridization or by unknown internal causes, and of the latter cases, we call 
mutation. 
It is a comparatively simple matter to determine the number of genes 
concerned with given characters by hybridization experiments when the 
contrasting characters are distinct and the segregation in the offspring of the 
hybrid is sharply defined. But it is extremely difficult to interpret those 
genes in terms of biochemistry or physiology. We are likely to fall into the 
danger of providing a superficial analogy and drawing sweeping conclusion by 
confusion of the genetical data to those of physiology. 
In the case of the formation of anthocyanin and phlobaphene pigments 
in the plants studied, the genes C, O, R and P appear to govern certain 
groups of biochemical reactions in the sporophytic cells more or less in a 
distinct manner, yet we must have great reserve in referring these genes to 
any physiological factors. It is true that the peroxidase coexists with the 
pigment, and the normal oxygen relation is essential to the formation of the 
pigment, but these facts prove in no way to allow us in interpreting the 
complementary gene of the colour producing system in plant is exclusively 
relating to peroxidase. Even in the case of the formation of brown and 
reddish brown pigments, in which the oxidation of the chromogenic substance 
is an essential change, the direct inference of the gene to peroxidase or 
oxidase may deserve serious consideration. 
The formation of brown plant-pigments (phlobaphenes) resembles, as we 
have already seen in the preceding pages, that of melanin pigments in animals 
