THE MUTATED GENE 157 



by a visible action of their own. Many examples of this type 

 have been mentioned in the preceding pages. We have discussed 

 also the development of those genetic formulations into formula- 

 tions in terms of genie action, the theory of the balance or proper 

 tune of gene-controlled reactions. 



In this field, there is a considerable body of special facts which 

 may be significant in connection with the problems of this book. 

 Certainly not all cases of genie interaction can be discussed, as 

 this would amount to a review of all the details of special genetics. 

 ( )nly certain facts will therefore be mentioned that throw direct 

 light upon the problem of genie action or that have been found in 

 connection with studies devoted to this problem. 



As mentioned before, the colors of the hair of rodents represent 

 one of the characters that has been used for a study of genie 

 interaction since early Mendelian days. A considerable number 

 of facts have already been reported in other chapters (see page 

 88). Referring to these, we may now consider the additional 

 data that apply to the problem of genie interaction. Wright has 

 emphasized this side of the problem, and his analysis (1927) 

 is the most complete one. 



Wright's studies on rodent colors have been mentioned in 

 connection with the problems of multiple allelism (page 87) and 

 also in regard to the chemism of genie action (page 91). In 

 the same work, also, the interaction of different genes controlling 

 the skin color was studied. The main factors influencing 

 pigment belong to a black (sepia) series and to a yellow series. 

 There is, in addition, the albino series of allelomorphs, which has 

 been discussed; a dilution series; and others that control the 

 pattern of pigmentation. Altogether seven series of allelo- 

 morphic factors and many of their combinations are known. 

 The combinations of the albino series with sepia and yellow, 

 respectively, have already been reported (page 88), and Wright's 

 interpretation has been given (Wright, 1925). These same series 

 were combined with a dilutor, the pink eye factor p, the brown 

 factor b, and the dilution factor /; and the color grades were 

 measured with the color wheel. Among these effects the first 

 to be considered is the difference between the yellow and the 

 black series which is caused probably by the production of two 

 melanins. This production is, however, not completely inde- 

 pendent. Factors like b and p may act on yellow or sepia 



