388 JOHN H. GEROULD 



gene probably destroys xanthophyl, but leaves intact a pigment 

 derived from the blue-green component of chlorophyl proper, 

 called chlorophyl a. The nature of the physicochemical change 

 involved, however, will be the subject of further investigation. 



All the recent investigations into the chemistry of green pig- 

 ments in the hemolymph of plant-eating caterpillars that have 

 come to the writer's attention (e.g., Dubois, '09; Steche, '12; 

 Geyer, '13, and Przibram, '13) support the conclusion of 

 Poulton ('85, '93) that these green and yellow pigments 

 are absorbed into the blood without undergoing fundamental 

 changes. The different pigments, however, xanthophyl and 

 chlorophyllin (chlorophyls a and h) are not absorbed in equal 

 degree in the two sexes, according to Steche ('12) and Geyer ('13) 

 for, while the blood of the female receives both chlorophyllin 

 and xanthophyl in proportions similar to those that occur in the 

 normal leaf and is consequently in certain species greenish, 

 that of the male of the same species contains only modified 

 xanthophyl, or else none of these pigments whatever, and .is 

 accordingly yellowish or colorless. Thus, presumably, in the 

 male the cells of the walls of the intestine produce a metabolic 

 reaction upon these pigments, destroying chlorophyllin and in 

 some cases xanthophyl also, while the corresponding cells in the 

 female have no such effect.' That this breaking up of the green 

 pigment in the male is not due to an enzyme in the hemolymph 

 itself, and accordingly should be ascribed to the action of the 

 intestinal epithelium, is shown by the fact that mixing the blood 

 of the male with that of the female does not decolorize the latter. 



The blue-green mutant caterpillars of C. philodice, however, 

 are equally distributed between the two sexes, and the same is 

 true of grass-green larvae heterozygous for blue-green. In this 

 case xanthophyl is destroyed, not chlorophyllin, and the decolor- 

 izing gene is not sex-limited. Whether a sex-difference exists 

 between the blood pigment of the male and female in C. philodice 

 is still unknown to me. In the common cabbage butterfly,^ 



> A series of observations on P. rapae that I have recently made show well- 

 marked individual variations such as" Guyer has described, but those that I 

 observed were not sex-limited. 



