BIOLOGICAL RELATIONS BETWEEN CAROTINOIDS 189 



to a certain size, but these did not develop normal color. It is espe- 

 cially interesting that the larvae on the etiolated leaves, as well as 

 those on the green leaves, should have developed green color. Poulton 

 thought that this indicated that the pigment of the etiolated leaf is 

 closely related chemically to chlorophyll, but since the pigment of 

 the etiolated leaf is now generally regarded as consisting chiefly of 

 carotin, the explanation of the greening of the caterpillars must lie 

 in their failure to inhibit the development of chlorophyll from its pre- 

 cursors in the etiolated leaf. Poulton's experiments have been accepted 

 as having proved that caterpillars derive their green and yellow pig- 

 ments from their food. In fact, it is generally held at the present time 

 that all phytophagous insects derive their lipochromcs and chlorophyll- 

 like pigments from their food, and that the former, at least, are passed 

 on from the larvae to the adults. 



Gamble (1910) attempted to determine whether the pigments which 

 develop in the hypodermis of the young crustacean Hippolyte varians, 

 is derived from the food. The newly-hatched larvae of this species are 

 colorless with the exception of lines of red pigment on the hypodermis. 

 When the adolescent larvae are placed among green or red seaweeds, 

 the entire hypodermis will turn green or red in 48 hours. Gamble 

 placed the colorless adolescent Crustacea in the inner chamber of 

 double-walled glass vessels, and put a mass of green or red or brown 

 alga9 in the outer chamber and fed the Crustacea various foods, such 

 as etiolated Laminaria, red crab meat, colorless crab ovaries, and red 

 crab ovaries. At the end of several days the Crustacea had in most 

 cases developed a color similar to their surroundings rather than like 

 that of their food. The conclusion, therefore, seems justified that the 

 red, green and brown colors in Hippolyte are not derived from the 

 food. No observation seems to have been made, however, on the 

 yellow pigment which occurs in the chromatophores of the fully de- 

 veloped Crustacea. Gamble states that true yellow pigment is absent 

 from the chromatophores of the newly hatched larvae. 



In addition to the experiments of Sauermann, Poulton and Gamble, 

 there remains to be mentioned that of Dombrowsky (1904) who ob- 

 served that the milk of a goat was tinted by feeding it carrots, and 

 also that of Moro (1908) who noticed a tinting of the skin of children 

 fed bountifully on carrot soup. The actual transference of carotin 

 from the food to the tissues and secretions of man and the higher 

 animals is at least indicated, although not demonstrated, in these cases. 



The writer's attention was attracted to a possible biological rela- 



