206 Cytoplasm as beat of Genetic Properties 



completely, a process which increases during the different molts. Two 

 extreme genetic types are a Japanese race with a bright pattern and 

 no overlying cuticular pigment, and a European race with so much 

 overlying pigment that even the young caterpillars do not show the 

 bright pattern. The factor for cuticular pigment may be called AA, 

 and its allele without production of this pigment aa. AA individuals 

 are grayish black; aa is bright-patterned. The largest bright spot may 

 be classified according to its size, and the variations produced by the 

 amount of covering with dark pigment can be expressed in a curve of 

 variation. If we consider only the crosses with the brightest and 

 darkest race — those with intermediate degrees gave the same results, 

 though less clearly demonstrable — Fi AA X aa is much darker than 

 the reciprocal aa X AA; that is, Fi is matroclinous. In F2 (correspond- 

 ingly RF2) the segregation AA:2Aa:aa occurs; this, in view of the 

 fluctuation, results in a curve of pigmentation with one mode in the 

 dark classes comprising about 25 per cent of the individuals and 

 another mode covering the 75 per cent in the medium and light 

 classes, which overlap. In reciprocal F2 crosses, however, these curves 

 are not identical but they are still matroclinous: with the dark 

 maternal grandmother the lighter part of the curve is shifted toward 

 the dark end; but with the light maternal grandmother it is shifted 

 toward the light end. The accompanying diagram illustrates this 

 (numerous exact curves and tables in the paper of 1924). 



25% 75% 



Since the same results were found (more or less clearly, ac- 

 cording to the differences between the parental races ) in a number of 

 different racial crosses, they may be regarded as typical for this 

 material. Moreover, Kiihn (1927) described a close parallel in Hahro- 



