150 TOILERS IN THE SEA. 



very elastic, with joints at short and regular inter- 

 vals. The little animals soon die, when removed 

 from their native element, and shrivel within the 

 tubes. For the most part the 'polyparies, or homes 

 of the polyps, are of a yellowish or horny colour, 

 and when immersed in water recover speedily their 

 original form, and elasticity. The material of which 

 this sheath is formed is called chitine, which resem- 

 bles horn in many particulars, but differs from it in 

 its chemical composition. It would be more accurate 

 therefore to describe these polyparies as branched, 

 chitinous, amber-coloured tubes, which shelter and 

 protect the polyps, or little animals, which inhabit 

 them. 



There are many forms, or species, of these zoo- 

 phytes, differing in the form of the polypary, or in 

 some minute detail, of the animals which dwell in 

 them. Some kinds prefer shallow, others deep water. 

 Some attach themselves to the rocks, others to shells, 

 or the larger seaweeds, and again some of the 

 smaller are parasitic upon the larger species. Each 

 kind, or species, has its own peculiar habit, which, for 

 our present purpose we need not particularise. In 

 some species the polypary is solitary, or scattered 

 singly over the rock, stone, or shell, whilst in others it 

 forms dense tufts ; but these are minute details which 

 do not influence the general observations it is our 

 province to offer ; this object being to present, with 



