PBELUnNARY OBSERVATIONS. 13 



forming polypes ; the jelly-fish and sea-nettles ; 

 the polygastric animalcules; the sponges, and 

 the tapeworms and hydatids. In this sub- 

 kingdom, the body of the various animals it 

 embraces consists of an apparently homogeneous 

 gelatine, often investing a framework of solid 

 material, often inclosed in tubes sometimes 

 simple, sometimes beautifully frondescent; in 

 other cases, it has no support: in some in- 

 stances, the animals move freely at pleasure, in 

 others they are fixed and have a plant-like 

 existence. Some species are simple ; others 

 form, by a vital union, a compound being, 

 consisting of myriads of polypes, each distinct, 

 yet all united into a whole by means of fila- 

 ments, or a common gelatinous support. lu 

 some groups, we behold a number of bodies of 

 a definite figure linked in floating chains to- 

 gether, but by a tie so slight that it is not easy 

 to understand the natixre of the union between 

 them, or determine precisely whether this 

 union be necessary for their individual vitality 

 or not. In some groups a digestive laboratory 

 is evident; in others mere canals traverse the 

 gelatine through which the absorbed fluids 

 circulate, till they are carried to a central 

 cavity, and this is ac once the apparatus of 



