ANNELIDA. 85 



breathe by the general surface of their bodies, and 

 have no special respiratory organs visible externally ; 

 these, therefore, have been called Abranchia,* with- 

 out gills. 



In a second division, the breathing apparatus con- 

 sists of a series of tufts (Fig. 63) or fringes arranged 

 along the middle or on each side of the back : these 

 are the DorsibrancMata.f 



In the third order, Tubicola,+ the Annelids inhabit 

 a tube either composed of shell or manufactured by 

 the agglutination of various materials. These have 

 their branchias in the form of plumes or branching 

 filaments attached to the head or neck (Fig. 65). 



First Order — Abranchiate Annelidans. 



This order comprehends two families, which differ 

 widely from each other. The Setigera,§ which have loco- 

 motive appendages in the shape of delicate spines or 

 bristles (^Earthworm, Net is) ; and the Suctoria,|| which are 

 destitute of such appendages, but are furnished instead 

 with a prehensile sucker, attached to each extremity of 

 the body (Leeches). 



TJie Eartk-worms (Lumhricus). The common well-known species 

 (Lumbricns ttrrestris, attains nearly a foot in length, its body is 

 composed of 120 riugs or more, and is completely destitute of eyes 

 or tentacles. Though a humble and despised creatm-e, the earth- 

 worm is a most important item in the economy of nature. Piercing 

 the ground in every direction, the earth is lightened by the united 

 labours of their countless legions, and thus they materially conduce 

 to its fertility. It consumes upon the sui-fiice of the ground, where 

 they soon become injmious, the softer parts of decaying vegetable 

 matter, and conveys beneath the soil the more woody fibres, where 

 they moulder and form the nutriment of living vegetation. Thus 

 eminently serviceable to the agriculturist, it likewise constitutes an 

 indispensable article of food for innumerable creatures belonging to 

 every order of creation ; and perhaps is a solitary instance of an 

 individual race subjected to universal destruction. The very emmets 

 seize it when disabled, and bear it away as a prize : it constitutes 



* A " not,*' and branchia, a gill. 

 [ Dorsum, the hack ; branchia, a gill. 

 X Tubus, a tube ; colo, I rnhahit. 

 § Seta, a bristle ; gero, I carry. 

 11 Suctorius, sucking. 



