ANNELIDA. 217 



full length (Jig. 91, 6), an arrangement well adapted to hold and 

 perhaps to crush their prey. 



But the most formidable jaws are met with in some of the 

 Nereidiform species, as in Leodicea antennata, of which a figure 

 is given above (fig. 77). When the proboscis of one of these 

 creatures is slightly everted, the extremities of three pairs of 

 strong horny plates emerge from the mouth ; of these, one pair 

 terminates by forming a powerful hooked forceps, while the others 

 present strong denticulated margins (fig. 92, A, a, 6, c). The 



Fig.92. 

 B A 



N 



nature of these teeth will be better seen by a glance at B in the 

 same figure, where they are represented upon an enlarged scale, 

 as they appear when detached from their connections. 



(261.) The alimentary canal of the Dorsibranchiate Annelidans 

 offers little which requires special notice. It invariably passes in a 

 direct line from the termination of the proboscis to the anal extremity 

 of the body. In the Nereidte it is provided with numerous lateral 

 pouches, somewhat resembling those of the leech. In Aphrodite 

 these lateral cseca are very long, slender, and branched at their 

 extremities, so that they have been thought by some to be secret- 

 ing organs, representing the liver. In Arenicola we find at the 

 termination of the oesophagus (fig. 94, f) two large csecal ap- 

 pendages (e) of unknown office, while the rest of the tube (c) is 

 entirely covered with minute sacculi, the walls of which are de- 

 cidedly glandular, and secrete a fluid of a greenish-yellow colour. 



(262.) The course of the principal trunks of the circulating system 

 in the Dorsibranchiata bears a general resemblance to what we have 

 already seen in the Abranchiate order, modified, of course, by the 

 variable position of the branchial tufts ; but with respect to the 



