372 JOHN r. FULTON, JR. 



observaiiou of raul and Sliarpe (1919) is of iiitorost. Thoy have 

 shown that iminodiately before the moult the contents of the 

 Hver greatly increase in quantity, and after the moult the amount 

 returns to normal. This would certainly affect the amount of 

 pigment free in the blood. G. W. Smith (1913) has called 

 attention to the fact that the amount of red pigment (which he 

 calked ' tetronerythrin ') varies in the female (crab) during 

 periods of reproduction, being most abundant shortly before 

 the eggs are produced. 



Before proceeding to the consideration of carotin a word 

 should b(^ said concerning the red pigment, tetronerythrin. 

 This substance was first described by Wurm (1871), who 

 reported that it existed in several animals. Merejkowski 

 (1881) reinvestigated the pigment, and came to the conclusion 

 that it was widely distributed throughout the animal kingdom, 

 since he found it in every phylum. Merejkowski's criteria for 

 tetronerythrin (also known as zooerythrin) are as follows : 

 the substance must be (1) insoluble in water ; (2) soluble both 

 in alcohol and ether ; (3) blue in acid ; (4) red in carbon 

 disulphide ; and (5) decolorized by light. Both Merejkowski 

 and (lautier held the pigment to be respiratory. In a later 

 paper, Merejkowski (Krukenberg) reported that he had demon- 

 strated zooerythrin in 117 species. Krukenberg^ found it 

 also on the eye-lids of birds and in their feathers. MacMunn 

 (1889), however, showed that a number of different pigment 

 substances would respond to the tests used by Merejkowski. 



The substance which responds to the test for tetronerythrin 

 in crustaceans is the red lipochrome described by Halliburton 

 (Halliburton, 1885 ; MacMunn, 1889), and, as tetronerythrin, 

 it has been extracted both from the epidermis and from the 

 blood ; this further substantiates the conclusion reached 

 above, that the red lipochrome of the blood is identical with 

 that of the chromatophores. In addition, MacMunn also held 

 that tetronervthrin arises in the liver. 



Carotin. — This substance is a yellow pigment found in 



^ Vergleith. physiol. iStuclien, Abth. o, and (2. Reilie) Abth. 1, p. 151 ; 

 Abth. 3, p. 128. 



