248 ANNELIDA. 



hension, formed by two horny hooks (fig. 119, B, a, 6) placed upon an 

 elevated ridge near the entrance of the oesophagus, so as to take a 

 secure hold of any victim seized by this curious mouth. 



(647.) In Phyllodoce laminosa the teeth form a circle of semicarti- 

 laginous beads encompassing the extremity of the proboscis when that 

 organ is pushed out to its full length (fig. 120, 6), an arrangement 

 well adapted to hold and, perhaps, to crush their prey. 



(648.) But the most formidable jaws are met with in some of the 

 Nereidiform species, as in Laodicea antennata, of which a figure is given 

 above (fig. 118). When the proboscis of one of these creatures is 

 slightly everted, the extremities of three pairs of strong horny plates 



Fig. 121. A 



Jaws of Laodicea antennata. 



emerge from the mouth : of these, one pair terminates by forming a 

 powerful hooked forceps, while the others 'present strong denticulated 

 margins (fig. 121, A, a, 6, c). The 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 con- 

 nexions. 



(649.) 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 Nereidce it is provided with numerous lateral pouches, somewhat 

 resembling those of the Leech. In Aphrodite these lateral ca3ca are very 

 long, slender, and branched at their extremities, so that they have been 

 thought by some to be secreting organs, representing the liver. In 

 Arenicola we find, at the termination of the oesophagus (fig. 128, /), two 

 large csecal appendages (e), of unknown office, while the rest of the tube(c) 

 is entirely covered with minute saccoli, the walls of which are decidedly 

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



(650.) In the majority of the Annelids, observes Dr. Williams, the 

 alimentary system constitutes a cylindrical tube, which bears a general 

 resemblance of outline to the integumentary, this latter forming, with 



