COMPOUND POLYPES. 77 



substance and dirty-white colour, flat, and built up of 

 innumerable little oblong cells, placed back to back, 

 like those of a honeycomb, and each crowned (as may 

 readily be seen with the help of a pocket-lens) by four 

 stout spines. It is these spines which give the surface 

 of the Polypidom (as the plant-like body is called) its 

 peculiar, rough, or harsh feel, observable if the finger 

 be passed over the surface from the apex towards the 

 base. 



This structure of cells (polypidom, or leafy-body) is 

 not the remains of a single animal, but of a community 

 of individuals as numerous as those of one of our cities, 

 each of which dwelt within the narrow compass of one 

 of the cells, in which he was born, lived, and died. This 

 cell was his house, more literally his skin, within which 

 he enjoyed an independent existence, at the same time 

 that he was linked, by a common circulation, to the 

 cells above and below him ; and thus had a double ex- 

 istence, being at the same time himself, and a part of 

 "the neighbours ;" or rather, a part of the compound 

 animal represented by the polypidom itself, and whose 

 individuality is exhibited by the regularity of its 

 growth ; just as a plant, which may be considered as a 

 community of separate leaves, proves its individuality by 

 the orderly manner in which those leaves are arranged. 

 The life enjoyed by this common Flustra may be taken 

 as an example of that of a class of animals to which it 

 is related, the compound Polypes whose remains, recent 

 and fossil, constitute an enormous portion of the fossil- 

 ized crust of the earth. The general form and structure 

 of the individual Polypes may be illustrated by the 



