BLUE-GEEEN CATERPILLARS 407 



It is of course not possible to say at present that the bkie-green 

 pigment of the blood and integument of the mutant is identical 

 with chlorophyl a, for certain changes may have occurred in 

 digestion of the chloroplastids and recombination of the pigments 

 with proteids dissolved in the hemolymph, but Poulton's ('85) 

 studies show that spectroscopically the pigments of normal green 

 caterpillars appear to have suffered no fundamental change from 

 the mixture of chlorophyl and xanthophyl that make up ordinary 

 leaf -green. 



Dr. William Patten, on looking at the mutant caterpillars, 

 was immediately impressed with the similarity between their 

 color and that of well-oxygenated hemocyanin as seen in the blood 

 of Limulus. A close comparison between the two was accord- 

 ingly made. It was found that the greenish hue that occurs 

 in th^ mutant caterpillar's blood is lacking in hemocyanin 

 though both, until brought together for comparison, look much 

 alike. 



The resemblance is interesting, in view of the well-known 

 chemical similarity of the animal and plant pigments concerned 

 with respiration and photosynthesis. Hemocyanin, hemoglobin, 

 and chlorophyl are chemically closely related. They have definite 

 chemical interactions with CQ2 and O, and their decompo- 

 sition products, hematoporphyrin from hemoglobin and phyllo- 

 porphyrin from chlorophyl, are almost identical. The possi- 

 bihty is at least worth investigating whether the chlorophylloid 

 pigments of the blood of caterpillars, though not respiratory 

 in the same sense as hemoglobin and hemocyanin, may not 

 perform some function in connection with the elimination of 

 CO2. The caterpillar's hemolymph is acid, as Poulton ('85) and 

 Mayer ('97) have shown, which may be due to the presence of 

 CO2. Moreover, Mayer pointed out that in an atmosphere of 

 CO2 the hemolymph does not coagulate. There is no direct 

 positive evidence, however, known to the present writer that 

 this green blood pigment is a reducer of CO2 or performs such a 

 supplementary respiratory function as that just suggested. 

 If such a reaction occurs, it cannot depend, as in photosynthesis, 



