TEREBELLA. 197 



euce 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 Terebellse, 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. 



This species can resume possession of the tube several hours after 

 having forsaken it. 



The Tercbella Jigulus is not 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. 



PLATE XXVII. 



PIG. 1. Terebellafigulus, mouth, a ; branchiae, b ; tontacula c The upper 



part of the belly is in front, and the branchiae behind. 

 2. One of the branchiae enlarged. 



PLATE XXVIII. 



FIG. 1 . Branchiae, magnified, 



2. Terebella figulus, smaller specimen, back. 



/x 



o. TEREBELLA TUBEHCULATA. Plate XX^Tf Figs. 1, 2. ; Plate XXVI. 



Fig. 8. 



This is one of the larger and most beautful of the Scotish Terebellae, 

 and if rarity has any value, it has herein a recommendation. 15ut, as 

 elsewhere adverted to, that is rather an imaginary than a real quality, 

 being often accidental. 



