
TEREBELLA. 197 
ence of instinct is extremely obscure in an animal exhibiting such an in- 
satiable propensity for exhausting its materials. It would rather seem 
to be influenced by some kind of necessity ; nevertheless its procedure is 
an act certainly consequent. on some comparison of circumstances, to 
which its labour is modified or adapted. 
The sense of feeling seems to regulate the discriminative faculties of 
this and other Terebellz, whence the sand, the mud, or the comminuted 
shell is selected in preference. The presence of the other senses is less 
evident, and that of vision the most obscure of all. Nevertheless, dur- 
ing the day, a simple wave of the hand will sometimes induce the tenant 
to retreat within its dwelling, which can be scarcely ascribed to any 
thing but interception of the light. p 
This species can resume possession of the tube several hours after 
having forsaken it. 
The Terebella figulus isnot common. Although the food be unknown, 
specimens live for a considerable time in confinement. That represented, 
Plate XXVI., which afforded the most satisfactory results, survived four 
months. Yet so little is derived from individuals preserved with all possible 
care, that the preceding brief details are the accumulation of many years. 
Prats XXVIII. 
Fig. 1. Terebella figulus, mouth, a; branchiz, 6; tentacula c. The upper 
part of the belly is in front, and the branchiz behind. 
2. One of the branchie enlarged. 
Prats XXVIII. 
Fic. !. Branchiz, magnified, 
2. Terebella figulus, smaller specimen, back. 
§ 3. TrREBELLA TUBERCULATA.—Plate XXVII. Figs. 1, 2.; Plate XXVI. 
Fig. 8. 
This is one of the larger and most beautful of the Scotish Terebelle, 
and if rarity has any value, it has herein a recommendation. But, as 
elsewhere adverted to, that is rather an imaginary than a real quality, 
being often accidental. 
