Serpulid.e. - 



-ANNELIDA.- 



-Sabeli.abiid.e. 



299 



are neither anteniiEe, eyes, proboscis, nor jaws visible 

 on the crown, or ou a lobe above the moutli, or on 

 each side near the mouth. On the anterior segment 

 of the body we see in most of the species a series of 

 filiform extensile tentacles, and on the first two or three 

 segments the branchice are placed. These organs are 

 few in number, are large, much branched, plumose, or 

 pectinated; and are arranged along the sides, rarely on 

 the middle of the back of these anterior segments : 

 Kometimes they are wanting altogether. The feet are 

 distinct, but not projecting or fitted for enabling the 

 animal to walk, as in tlie preceding order. They are 

 not uniform in structure, but present a difl'erent appear- 

 ance in different parts of the body. They are biramous, 

 enlarged transversely, and armed with the ordinary 

 setaceous bristles, as well as with booked bristles or 

 uiicini, which serve the animal for moving up and 

 down in its tube. The mouth is terminal and placed 

 transversely. Some of these Annelides form a homo- 

 geneous calcareous tube, which is generally attached to 

 a stone, rock, or shell, &c. Others construct tubes by 

 agglutinating grains of sand, fragments of shells, and 

 liarticlea of mud, which they join by means of mem- 

 brane. A third set, again, inhabit tubes which are 

 entirely membranous or horny. 



Family I.— SERPULID^. 



The animals belonging to this family have an elon- 

 gateil, worm-shaped body, divided into short segments 

 and distinguishable into thoracic and abdominal por- 

 tions. The head is amalgamated with the following 

 segments, and not noticeable in the adult. The first 

 segment is encircled with a collar, which is said to be 

 the part of the body that secretes the shelly tube. It 

 is also furnished with a tuft of bristles on each side. 

 The feet are composed of tivo branches. In the thoracic 

 portion of the body the dorsal branch is armed with 

 setaceous bristles, while the ventral is furnished with 

 hooked ones. In the abdominal portion of the body 

 (which is the longer) it is the ventral branch that is 

 armed with the setaceous, and the dorsal with the hooked 

 bristles. The branchia; are attached to the vertex or 

 first segment, consist of two divisions, and resemble 

 a fine plume in shape of a fan, and are, in general, 

 adorned with the most lively colours. Each of these 

 divisions consists of a pedicle, the upper edge of which 

 is furnished with a great number of filaments placed in 

 a line, like the teeth of a comb, and each in their turn 

 provided with a double row of movable barbules. 

 Though these branchiae serve the purpose of respiratory 

 organs, it would appear, says Audouin, that it is not 

 the only use to which they are applied; for Bosc hos 

 observed that these animals live on small worms, which 

 they attract to their mouths by the whirlpool caused by 

 the rapid motion of these organs in the water. — Scr- 

 piiki cortortiqilicciia (fig. 205) will illustrate the family. 



F.\MiLy IL— TEREBELLID.^:. 



In general form the animals of this family resemble 

 very much the preceding, being vermiform and cylin- 



drical, without distinct head, and divided into thoracic 

 and abdominal portions. The feet on the thoracic 

 portion are similar to those of Serpulido', but on the 

 abdominal portion the dorsal bristles, or both dorsal 

 and ventral, are frequently wanting. The branchiiB 

 are pectinated or much branched, rarely filiform, and 

 placed laterally. These animals inhabit membranous 



Fig. 205. 



Serpula cortortuplicatft. 



tubes, which are coated with particles of sand, gravel, 

 or broken shells agglutinated together, and open at 

 both extremities. 



F.iMiLY III.— SABELLARIID^. 



In this family the body of the animal is composed 

 of few segments, and is divided into two distinct por- 

 tions. The anterior portion has the segments provided 

 with setigerous and uncinated feet ; the posterior is 

 narrow, without segments, and witliout feet, more like 

 a caudal appendage. The first segment is large and 

 truncate, disc-shaped, and having an operculum com- 

 posed of several rows of flatfish bristles. The mouth 

 is placed in the centre of this disc, and encircled with 

 a somewhat extensile lip. The feet are in two series ; 

 the upper prominent, armed on some of the anterior 

 segments with flat, or sometimes hooked bristles, and 

 on the following segments with small fascicles of capil- 

 lary bristles. The branchia; are in pairs on all the 

 segments. 



