164 CAROTINOIDS AND RELATED PIGMENTS 



served by the other investigators was due to the action of light on 

 the red pigment. The properties of the yellow pigment which show 

 its probable carotinoid nature are its solubility in alcohol, ether, 

 petroleum ether, chloroform and carbon disulfide, its color being 

 orange red in the last named solvent; its resistance to saponification; 

 its lipochrome color reactions with the concentrated mineral acids; 

 its two-banded absorption spectrum; and the great ease with which 

 the pigment bleaches. As to whether the pigment is carotin or 

 xanthophyll we have only the measurements of the absorption bands 

 of the "lutein" which MacMunn (1883) extracted from the liver of 

 the crab, Cancer pagurus, and of the "yellow carotin" which Zopf 

 secured from the little Diaptomus crustacean. MacMunn gives the 

 measurements in ether as 498-480^1 and 466-450|i|i, and in CS 2 as 

 530-507nn and 496-476u^i. Zopf s "yellow carotin" in petroleum ether 

 showed bands at 498-479|i[.i and 464-450ii[.i. The agreement exhibited 

 in like solvents indicates that these investigators were dealing with 

 the same pigment. The position of the bands suggests carotin rather 

 than xanthophyll. 



As is well known, the red color so frequently associated with Crus- 

 tacea is apparently absent from the external tissues until the appli- 

 cation of heat produces the usual brilliant red hue. The common 

 lobster is a conspicuous example. The shell of this animal is very 

 dark blue, although the underlying hypodermis is red. In the case 

 of the fresh water crayfish, Astacus nobilis, the shell is grayish brown 

 and the hypodermis blue. The salt water crayfish or Norway lobster, 

 Nephrops norwegicus, has an orange shell and red hypodermis. Green 

 colors are also seen, as in the species Virbius viridis. Blue colors 

 are found among the Copepods, also, Merejowsky (1883) mentioning 

 the species Anemalocera Patersoni and Pontellina gigantea. The 

 very fugitive character of these blue colors has been known for many 

 years. Not only heat, but reagents like alcohol, ether, or acids change 

 the color of the tissues to the characteristic red. Pouchet (1876) 

 believed that the phenomenon was due to the destruction of a very 

 unstable blue pigment which then allowed previously invisible red 

 pigment to be seen. Krukenberg (1882k), however, advanced the 

 theory that the blue and green colors were due to lipochromogens 

 which were transformed by the various reagents into lipochromes. 

 This theory has been adopted by nearly all subsequent investigators, 

 including Merejowsky (1883), MacMunn (1890) and Newbigin 

 (1897). Merejowsky called the lipochromogen velelline, after Negri, 



