156 TOILERS IN THE SEA. 



question, we may observe that the polyps, which are 

 attached to the common body, are those which suck 

 in the nutriment for the support of that body, whilst 

 the reproductive animals, or those which are con- 

 cerned in the perpetuation of the species, soon 

 become free, quit their old home, and go forth to 

 establish a new one, being in themselves the unit 

 from whence a new colony is to spring. For the 

 present we are concerned only with the fixed polypes, 

 the members of a given colony, who toil for the 

 sustenance and support of the commonwealth. This, 

 which is the true polype, consists of a digestive sac, 

 with a terminal mouth, surrounded by tentacles, and 

 is attached, at the base, to the extremity of one of 

 the branchlets of the common trunk (c&nosarc). The 

 soft body is very contractile, and consequently vari- 

 able in form, attenuated when thrust out at the 

 openings of the horny sheath, and broader when 

 withdrawn and contracted. The hollow cavity in 

 the centre is a sort of simple stomach, ending up- 

 wards in an opening, or mouth, and continued below 

 into the common canal, which traverses all the 

 branches, down to the main trunk. The mouth is 

 sometimes a simple, and sometimes a lobed opening, 

 surmounting a sort of proboscis, which is either 

 conical or funnel-shaped. It is an admirable little 

 instrument for the acquisition of food, the lips 

 opening and closing as occasion requires. The 



