IV THE COLOURS AND PIGMENTS OF CCELENTERA 8i 



accompanied by a process of contraction which not 

 infrequently destroys all beauty of form as well as of 

 colour. All these causes combine to render it practi- 

 cally impossible, at least with present methods of 

 technique, to adequately preserve the large majority 

 of the Coelentera. Frequenters of museums will 

 recall the glass models or crudely tinted chromo- 

 lithographs which usually fill the cases devoted to 

 the group. Although, therefore, the beauties of the 

 coral-reefs must to most of us be merely a matter of 

 hearsay, yet it should be emphasised that Coelentera 

 are inhabitants of temperate as well as of tropical seas, 

 and that many a pool on the British coast will dis- 

 play organisms whose colouring differs in degree 

 only, and not in kind, from that of the denizens of 

 the most marvellous coral-reef 



It is not necessary here to discuss the structure 

 of the Coelentera ; we need only recall the fact that 

 most of the organisms included in this class are either 

 polypes of the nature of a sea-anemone, or jelly-fish 

 of the familiar type, and that both these forms may 

 occur in the course of a single life-history. For our 

 purpose it is sufficient to think of a polype as con- 

 sisting of a hollow column fixed at one end to some 

 solid body, and bearing a mouth surrounded by 

 waving contractile tentacles at the free end. Such 

 polypes may grow singly as do the sea-anemones, or 

 they may grow together in " colonies." The polypes 

 in such colonies are connected together by a fleshy 

 substance traversed by numerous tubes. If lime be 

 laid down in considerable amount in this fleshy 

 substance, the colony forms a " coral." This " coral " 

 or limy skeleton is really outside the individual 



G 



