VI COLOURS OF CRUSTACEA AND ECHINODERMA 135 



Moseley discovered in several species of Pentacrinus 

 a complex pigment, which he called pentacrinin. 

 We have already mentioned the variations in colour 

 which his specimens presented. He found that the 

 purple specimens yielded a pigment which formed a 

 pink solution in acidified alcohol, the solution turning 

 blue-green with ammonia. Both solutions yielded 

 banded spectra differing in the two cases. Pale or 

 yellowish -coloured specimens, on the other hand, 

 yielded a green solution to alcohol, but the solution 

 turned pink with acid, and apparently contained the 

 same pigment as the purple specimens. Moseley 

 suggests that the reaction of these specimens was 

 probably alkaline during life, and that the pigment 

 was therefore present in its alkaline form. Curiously 

 enough Moseley obtained another specimen of Penta- 

 crinus in which the complex pigment was entirely 

 absent, and a lipochrome only was found. It is, 

 however, probable that the purple specimens con- 

 tained a lipochrome mixed with the pentacrinin. 



The species of Antedon show similar variations in 

 the nature of their pigments. In Antedon {Comatuld) 

 rosacea, Krukenberg describes yellow, red, and brown 

 pigments, all nearly related to one another, and all 

 soluble in water; they do not give banded spectra. 

 In another Antedon Moseley found a purple pigment 

 which he calls antedonin. It formed in alcohol when 

 dilute a pink solution which turned orange with acid 

 and violet with ammonia, and gave banded spectra 

 differing in the different conditions. These two 

 peculiar pigments, antedonin and pentacrinin, re- 

 semble in several respects the pigments of the 

 enterochlorophyll or chaetopterin group, but have not 



