STRUCTURE OF THE BARNACLE. 25 



closed ; d, the mouth, with its fleshy aerating- processes 

 E, E. F is the conical termination of the body ; g are the 

 tentacula, or many-jointed arms, set on their peduncles. 

 These arms are covered with a slightly horny investment, 

 and at each joint are furnished with hair-like append- 

 ages, forming a sort of fringe. 



The animals can retract or protrude these organs at 

 pleasure, and move them about with great facility ; it 

 is by their means that the seizure of food is effected. 

 Their delicacy of touch is extreme ; they feel the con- 

 tact of the minutest bodies, and enfold them in their 

 grasp. WTiile the barnacle is on the watch for its 

 prey, these many-jointed arms are all protruded, and 

 are themselves, together with their fringes, in per- 

 petual motion, acting the part of a sweeping-net. The 

 moment some minute tenant of the water is touched, 

 it becomes entangled in their folds, is carried to the 

 mouth, is there crushed by the jaws, and trans- 

 ferred to the stomach. WTien fully expanded and 

 in motion, these arms present a very elegant appear- 

 ance : besides being organs for the seizing of food, 

 it is very probable that they are also agents in the 

 aeration of the circulating fluid, co-operating with the 

 fleshy oral processes, regarded as exclusively employed 

 for this important purpose in the service of this animal. 



