50 Colouration in Animals and Plants. 



The other sub-kingdoms are : — 



Coslenterata, of which the jelly-fishes are a type ; animals possessing 

 an alimentary canal, fully communicating with the general cavity of 

 the body, but without distinct circulatory or nervous systems. 



A nnuloida, of which the star-fishes are a type ; animals having the 

 alimentary canal shut off from the body-cavity, and possessing a 

 nervous system, and in some a true circulatory system. 



Annulosa, of which worms, lobsters, and insects are types; animals 

 composed of definite segments, arranged serially, always possessing 

 true circulatory and nervous systems. 



Mollusca, of which oysters and whelks are types ; animals which 

 are soft-bodied, often bearing a shell, always possessing a distinct 

 nervous system and mostly with a distinct heart. 



In old systems of classification, the Coslenterata and Annuloida 

 were united into one sub-kingdom, the Radiata, in consequence of 

 their radiate or star-like structures. 



As colouration, according to the views here set forth, depends 

 upon structure, we may classify the Invertebrata thus : — 



Radiata. Radiate structure. 



Protozoa ... ... ... Structureless. 



Coelenterata 



Annuloida 



Annulosa ... ... ... Segmented „ 



Mollusca ... ... ... Marginate „ 



The mollusca are said to be marginate in structure because, in those 

 possessing shells — the mollusca proper — the shell is formed by suc- 

 cessive additions to the margin or edge of the shell, by means of the 

 margin of the mantle, or shell-secreting organ. 



Now we shall proceed to show that the schemes of colouration 

 follow out these structure-plans, and thus give additional force to 

 the truth of the classification, as well as showing that, viewed on a 

 broad scale, the present theory is a true one. 



We can, in fact, throw the whole scheme into a table, as 

 follows : — 



