CHAPTER IX 
THE COLORATION OF MOLLUSCA AND OF 
INVERTEBRATES IN GENERAL 
Colours of the Mollusca: (i) of the Mantle, (2) of the Shell, 
(3) of the Secretions—Pigments of the Mollusca—Green 
Oysters—Characters of Coloration of Invertebrates— 
Patterns and Markings of Organisms ; Plants, Ccelentera, 
Leeches, Arthropoda, Mollusca, Vertebrates—Meaning 
of Patterns. 
The Mollusca are especially remarkable for the 
number and brilliancy of their pigments; unfor¬ 
tunately, however, these have been relatively little 
investigated. The pigments occur especially under 
three circumstances—in the mantle, in the shell, and 
in the secretions poured out by many, of which the 
far-famed fluid of Purpura may be taken as a 
type. 
1. Colours of the Mantle .—The mantle-folds 
themselves, or the general body wall, are not infre¬ 
quently highly coloured, and this whether the coloured 
regions are visible during life or not. Thus Mr. 
Saville Kent describes the mantle of Tridacna com- 
pressa , the Frilled Clam, as being during life resplen- 
