CAROTINOIDS IN INVERTEBRATES 163 



at once shows the close relation of the pigment (o the carol inoids. 

 The chromatic colorations with the strong mineral acids arc also 

 identical with the earotinoid colorations under like conditions. How- 

 ever, unlike any of the known carotinoids it appears to form com- 

 pounds with the caustic alkalis, and alkali earth metals, and can, 

 moreover, be precipitated from its alcoholic solution on addition of 

 saturated Ba(OH) 2 , Ca(OH) 2 and Mg(OH) 2 solutions. The pig- 

 ment can be readily liberated from its alkali and alkali earth 

 compounds by acids, apparently without injury to its properties. 

 According to Maly and Newbigin these pigment compounds are insol- 

 uble in alcohol, but are soluble in ether, chloroform, carbon disulfide, 

 benzene and petroleum ether (slightly). Zopf, however, denied the 

 solubility of the calcium and barium compounds in any of these sol- 

 vents, and states that the sodium compound, only, is soluble in the 

 solvents mentioned. He noted, also, that the sodium compound, like 

 the free pigment, readily bleaches. Spectroscopically, as already men- 

 tioned, the pigment differs from the known carotinoids in that it shows 

 only one absorption band. According to Zopf this band in ether lies 

 at 515-465|4i and in carbon disulfide at 533-482u(i. 



In view of the unanimity of the above mentioned investigators on 

 the properties described one cannot help being somewhat surprised at 

 the recent announcement of Verne (1920a, b) that the red pigment of 

 Crustacea is none other than carotin. It is stated that the pigment 

 which he isolated in pure crystalline form from the hypodcrmis of 

 the Decapod Crustacea (lobsters, crabs, etc.) has the same melting 

 point, forms the same iodide, exhibits the same absorption spectra 

 and shows the same composition on analysis as carotin. It is true 

 that Blanchard (1890) called the impure red pigment which he iso- 

 lated carotin, but he was hardly justified in so doing inasmuch as his 

 pigment showed no absorption bands whatever. The findings of 

 Verne, therefore, while very significant, cannot be given unqualified 

 acceptance until it is possible to explain the peculiar properties which 

 were obtained by all previous investigators for this carotin-like 

 pigment. 



As for the yellow pigment we have the observations of Maly, Kru- 

 kenberg, MacMunn and Zopf, to determine its possible relation to 

 the carotinoids. Miss Newbigin's (1897) failure to confirm the lipo- 

 chrome characteristics of this pigment can only be explained on the 

 grounds that she was dealing with a decomposition product. There 

 is certainly no basis for her idea that the two-banded spectrum ob- 



