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THE A ME file AX X ATI' II All ST 



[Vol. LII 



These caterpillars always give normal moths and nor- 

 mal offspring. 



A careful consideration of these points shows clearly 

 what these multiple allelomorphs for pigmentation really 

 are : They are different quantities of the substance which 

 we call a gene which act according to the mass-law of 

 chemical reactions, i. e., produce a reaction or accelerate 

 it to a velocity in proportion to their quantity. In our 

 special case it means that the factor stands for a metabolic 



activity proceeding with a definite velocity dependent 

 upon the quantity of the factorial substance present. 

 This activity finds its visible expression in the deposition 

 in the skin of increasing quantities of certain products of 

 protein decomposition which as chromogens are oxidized 

 into melanin pigments. The effect of the different quan- 

 tities of active substance (enzyme?) which we call the 

 multiple allelomorphs upon the progressive pigmentation 



