148 CAROTINOIDS AND RELATED PIGMENTS 



One cannot leave the paper of Cunningham and MacMunn without 

 referring to the interesting experiments of Cunningham on the color- 

 less side of flounders. These interesting fish, as is well known, have 

 the habit of lying continuously on their left sides as near as possible 

 to the bottom of the sea, or the tank in which they may be placed. 

 The lower side of the fish is almost always devoid of the black and 

 yellow color which characterizes the upper side of the fish. Cunning- 

 ham, however, was able to cause the fish to develop normal pigmen- 

 tation on both sides by placing them in a tank with a glass bottom 

 with a light reflecting mirror below it so that the fish were exposed 

 to daylight on both sides. Cunningham and MacMunn naturally con- 

 cluded that it is light which causes the deposition of pigment in the 

 flounder's skin. There seems to be nothing to discredit this conclusion 

 so long as one accepts as proved that pigment is actually absent from 

 the colorless side of the flounder and that chromatophors in the 

 epithelial tissues play no part in the phenomenon. 



With regard to chromolipoids in other tissues of the fishes, informa- 

 tion is almost completely lacking. AVe have the observations of 

 Krukenberg and Wagner (1885) already referred to, of a red zoonery- 

 thrine in salmon muscle, changing to a rhodophane on saponification. 

 We also have the statement of MacMunn (1883) that the liver of 

 fishes may contain a tetronerythrine (zoonerythrine). Finally, we 

 have Miss Newbigin's (1898) examination of the red pigment in 

 salmon muscle, m which she found a yellow non-lipochrome pigment 

 as well as the red lipochrome, showing the usual lipochrome reactions 

 save the absorption bands. She believed that the red pigment readily 

 formed compounds with sodium and potassium, which could be decom- 

 posed with acetic acid. The yellow pigment was soluble in the fat 

 solvents, did not form compounds with sodium and potassium but 

 failed to show the color reactions with concentrated acids. The spec- 

 troscopic absorption properties apparently were not observed. The 

 same red and yellow pigments were also present in the ovaries of the 

 mature female. 



Carotinoids in Amphibians 



The phenomena governing the coloration of these vertebrates, as 

 well as the colors observed, are almost identical with those of fishes. 

 As in the case of the fish pigments, the chromolipoids offer an inter- 

 esting problem for study from the newer point of view of these pig- 

 ments. The observations which have been made from the older lipo- 



