IV THE COLOURS AND PIGMENTS OF CCELENTERA 93 



benzol, chloroform, phenol, heat, etc., destroy the blue 

 colour and give a precipitate of dull red or brown 

 colour. The blue solution in water gives three (or 

 two ?) bands in its spectrum, but Professor E. R. 

 Lankester (1870) did not succeed in getting these 

 bands with Vellela ; the reddish-brown substance 

 apparently gives no bands. Further, in Rhizostoma 

 Cuvieri the blue colour is somewhat variable ; it 

 chiefly occurs in young specimens ; the older, especially 

 when carrying eggs, are of dirty red or reddish-brown 

 tint. This must surely be due to the modification of 

 the unstable blue pigment under the influence of 

 some specific change in the chemical characters of the 

 protoplasm of the organism. Then again, Professor 

 M'Kendrick found that the brown colouring-matter of 

 the jelly-fish Chrysaora was soluble in hot sea-water, 

 yielding a dark brown solution of acid reaction, which 

 gave a reddish-brown precipitate with strong alkali. 

 It seems probable that this colouring-matter is also 

 the result of a modification of cyanein. 



These cases show that in all probability the 

 number and variety of the tints in the Ccelentera 

 are due in large part to physical or chemical changes 

 in a few complex pigments. As to the cause of these 

 changes, it must be noted that the pigments are here 

 deposited in internal structures where active meta- 

 bolism is going on, and not, as in many higher 

 animals, in superficial inert tissues. The physiology 

 of the higher Vertebrates shows that in them there is 

 a metabolism of pigment as active as any that can 

 occur in coral polypes ; but while in the latter every 

 change is apparent on the surface, in the former the 

 changes are concealed by the intervening passive 



