GENIC INTERACTION 



163 



in which log R w is the average logarithm of readings of white and R x in the reading in 

 question. A final intensity index was obtained from the sum of the indices from the 

 three filters. Relative quantities of pigment were estimated from the colorimetric 

 determination by way of the relations to the visual grades. Figures 23 and 24 are 

 based on such estimates for various genotypes; figure 25 is based on the unweighted 

 average of estimates from the indices and earlier estimates from visual grades. An 

 index of quality (Q) was obtained 1438 from the ratio of the index from the blue filter 

 to the total index (/). Average quality (Q) is plotted against average intensity (/) 

 for various genotypes in figure 26. 



The melanoproteins of the granules consist of melanoid derived by oxidation of 



Fig. 23. EUMELANIN AND PHAEOMELANIN IN GUINEA PIGS. 



c a c° c r c a c r c r c d c a c d c r c d c d c k c a c k c r c k c d c k c k C 



i 



c a c a c r c a c r c r c d c a c d c r c d c d c k a a c k c r c k c d c k c k c 



Estimates of amounts of eumelanin (100-intense black), above, and of phaeomelanin 

 (100-intense yellow), below, in guinea pigs with combinations of is, e; B, b; C, c k , c d , c T , c°; 

 P, p and F,f. The eumelanic estimates are based on animals with three or four plus factors 

 at the loci Si, si; Dm, dm. The phaeomelanic estimates are based on those with three plus 

 factors. The estimates are transformed from reflectionmeter readings. 



