280 



GENERAL CHARACTERS OF CIRRHOPODA. 



Entomostracous Crustacea (Fig. 606), that it would be im- 

 possible to show any decided difference between them. This 

 is a very interesting example of the importance of becoming ac- 

 quainted with the whole Natural History of an animal, whose 

 place in the scale is at all doubtful. 



SECTION E. 

 ORDER XIII. CIRRHOPODA. 



891. The Barnacles and their allies, composing this Order, 

 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 spongv muscular character which corresponds 

 with the mantle of the Mollusks ( 940). From its surface is 

 secreted a shell, composed of several pieces, but not differing in 

 general aspect from shells belonging 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 Mollusca are peculiarly adapted. 



892. 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 ( 936). 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. 



ThpP rirrfii nr fpnrlril-likp FIG. 613. RH..LL OF FIG. 614. BODY OP 

 neS6 Cirmi, Or tenaril-ilKe THE BAKNACLE. THEBAENACLK. 



organs, are long tapering 



arms, fringed with cilia, or little hair-like filaments, by the 



