84 ANNELIDES. 



(fig. 1,/) that indicate the power and cruelty of the species. No 

 acephalous Annelid has jaws of such strength ; and few have any 

 organs of the kind. The proboscis is occasionally roughened with 

 small horny prickles collected into clusters (fig. 1), or clothed with 

 minute fleshy papillse ; and its orifice is either plain or encircled 

 with tentacles (fig. 2, h). 



5. Feet. — In the majority of Annelides there is a foot on each 

 side of every ring which is armed with bristles, and provided with 

 certain soft appendages to which the names of cirri, branchiae, and 

 scales have been applied*. 



The foot in general is composed of two parts or branches placed 

 one above the other. These branches are sometimes wide asunder, 

 and easily to be distinguished into a dorsal or superior (No. VIII. 

 figs. 3, 4, «), and a ventral or inferior branch (b) ; but sometimes, on 



No. VIII. 



^d 



the contrary, they are intimately united, and appear to have coalesced 

 in one (fig. 5)f . Each branch is provided with a brush of bristles 

 (figs. 3, 4, 5, c), which the animal can protrude considerably from 

 the outer or distal end. 



The bristles are of two kinds, — the subulate and the hooked. 



The subulate bristles are distinguished into bristles (festucse) 

 properly so called (figs. 3, 4, 5, c), and into aciculi or spines {d). 

 The former are either grouped in brush-like bundles or arranged in 

 a fan-like series : their shape and structure are very variable. The 

 spines are stouter than the bristles, always straight and needle-like, 

 and deeper coloured. There is only one to each brush of bristles, 

 and it is enveloped in a proper sheath. 



The hooked bristles (uncinuli, No. X. fig. 9 b) are never met with 

 on the two branches of the same foot : they exist only in the Tubi- 

 coles^ and their presence is always coincident with a head indistinctly 

 developed or obsolete. They are disposed in one or two series, and 

 occupy the margin of a transverse fold or of a slightly raised mamilla. 

 Their arrangement in a more or less oval ring has given occasion to 



* On the structure of the foot, see De Quatrefages in Ann. des Sc. Nat. x. 

 (1848) 51. 



t I prefer to call the divisions of the foot branches rather than oars, as Savigny 

 and Blainvilie call them ; for the Annelides " with reptile motion creep," and do 

 not swim except when placed in untoward circumstances. Oersted names the feet 

 " pinnae," and each has its " pinna superior v. dorsalis," and its ** pinna inferior v. 

 ventralis." — Consp. Ann. Dan. p. 5. 



