86 ANNELIDA. 



by water, and which, being lifted up by two rows 

 of broad plates placed beneath it, allows the water 

 to filter through it, and to fill a large chamber 

 between it and the back, where it parts with its 

 oxygen through the delicate skin. 



No members of this Class have true jointed feet; 

 but most of them are furnished with pencils of 

 projectile bristles, which, pressing by their points 

 against surrounding objects, effect the purpose of 

 locomotion. These bristles are most exquisite 

 objects for microscopic observation, as they display 

 the greatest variety of form, constituting lances, 

 spears, knives, saws, sickles, hooks, and other inde- 

 scribable weapons, of innumerable elegant shapes, 

 often curiously jointed, and usually fashioned out 

 of an elastic material that rivals the clearest 

 glass. 



Almost all the tribe are carnivorous, and many 

 are predatory and ferocious. In general the mouth 

 conceals a great proboscis, which, at the time of 

 feeding, is rapidly turned inside out, and is in 

 many species armed with one or more pairs of 

 horny jaws. 



Localities, &c. Some of the Apoda are perma- 

 nently, and others are occasionally parasitic on other 

 animals; adhering to them by broad sucking- disks, 

 and extracting their vital juices. The Cephalo- 

 Iranchia for the most part inhabit tubes of their own 

 manufacture, which are either shelly, as those of 

 the Serpulce and Spirorles, or built up of grains 

 of sand, and fragments of shells, as those of the 

 Terebella, Pectinarite, and Sabellarice, or consist 

 of a membranous tough exudation from the body 

 of the animal, as in most of the Sabellae, the 

 Othonia, &c. Some of these attach their tubes to 



