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 ( Comatula ) 
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 chsetopterin group, but have not 
