CHAPTER XII. 



OF THE CLASS OF CIRRHOPODA. 



825. The Barnacles and their allies, composing this class, 

 have so many characters in common with the Mollusca, that they 

 have been generally regarded as belonging to that Sub-kingdom. 

 The body and its appendages are themselves quite soft ; and 

 the skin has the loose spongy muscular character, which corre- 

 sponds with the mantle of the Mollusks ( 868). From its sur- 

 face is secreted a shell, composed of several pieces, but not 

 differing in general aspect from multivalve shells ( 870) belong- 

 ing to that division. Further, these shells are either themselves 

 firmly united at their bases to rocks or solid masses, or they are 

 attached by a long peduncle or foot-stalk ; so that the conditions 

 in which the animals exist, closely resemble those to which we 

 observe the Mollusca peculiarly adapted. 



826. On the other hand, when we examine the animal itself, 

 we find that it is perfectly 



symmetrical in form ; a cha- 

 racter but rarely observable 

 amongst Mollusks that are 

 inclosed in shells of similar 

 nature ( 864). The body is 

 prolonged, and exhibits an 

 imperfect division into seg- 

 ments ; and from each of these 

 arises a pair of appendages on 

 each side, which possess some- 

 what of a jointed structure. 

 These cirrhi, or tendril-like 

 organs, are long tapering 

 arms, fringed with cilia, or 



FIG. 514. SHELL OK 

 THK BARNACLE. 



Fio. 515. BODY OK 



THK 11 \RNACLK. 



little hair-like filaments, by 



