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, Coelentera, 

 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. 



I. 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- 



