FOOD OF THE CIRRIPEDES. 393 



very different types, however, are comprehended under 

 this name, viz. the families of LEPADES or true Bar- 

 nacles (PL VII. fig. 6), and that of the BALANI or 

 Acorn-shells of British conchologists (PL VII. fig. 5), 

 the former elevated on a membranous pedicle, the 

 latter sessile, and provided with a domicile wholly cal- 

 careous : several species of both of them are amongst 

 the most abundant and common productions of the 

 ocean. The Balani attach themselves, for the most 

 part, to the surface of rocks, and are consequently 

 the inhabitants of the shore; the Lepades, on the 

 contrary, are seldom found on fixed bodies, but almost 

 always on such as float upon the surface of the sea, 

 such as Fuci, bits of wood, and the bottoms of ships, 

 by which means they participate in the benefits of a 

 vagrant life. 



The food devoured by the Cirripedes would seem 

 to consist of various minute animals, generally of 

 microscopic dimensions, caught in the water around 

 them by a mechanism at once simple and elegant. 

 Any one who watches attentively the proceedings of 

 a living Barnacle when in a vigorous and active con- 

 dition, will perceive that its arms, with their ap- 

 pended cirrhi, are in perpetual movement, being alter- 

 nately thrown out and retracted with great rapidity ; 

 and that, when fully expanded, their plumose and 

 flexible stems form an exquisitely beautiful apparatus, 

 admirably adapted to entangle any nutritious mo- 

 lecules, or minute living creatures that may happen to 

 be present in the circumscribed space over which this 

 singular casting-net is thrown, and drag them down 

 into the vicinity of the mouth, where, being seized by 



s5 



