352 CIRRHOPODA. 



perfection of the Mollusca, as regards their endowments and capabili- 

 ties. Some, as the Barnacles (CIRRHOPOUA), fixed to the surface of 

 various submarine bodies, either immoveably or by the intervention 

 of a flexible pedicle, entirely deprived of organs connected with the 

 higher senses, and unable to change their position, are content to 

 cast out at intervals their ciliated arms, which form a net of Na- 

 ture's own contrivance, and thus entrap such passing prey as suits 

 their appetite. Others, equally incapable' of locomotion, but fur- 

 nished with arms of different construction, (BRACHIOPODA,) catch 

 their food by similar efforts. The TUNICATA, enclosed in coria- 

 ceous bags, are firmly rooted to the rocks ; or, aggregated into 

 singular compound masses, float at the mercy of the waves. The 

 CONCHIFERA inhabit bivalve shells ; while the GASTEROPOD or- 

 ders, likewise defended in most cases by a shelly covering, creep upon 

 a broad and fleshy ventral disc, and, thus endowed with a locomotive 

 apparatus, exhibit senses of proportionate perfection. The PTE- 

 ROPODA swim in myriads through the sea, supported on two fleshy 

 fins ; while the CEPHALOPOD MOLLUSCA, the most active and 

 highly organized of this large and important division of animated 

 nature, furnished with both eyes and ears, and armed with formidable 

 means of destroying prey, become tyrants of the deep, and gradu- 

 ally conduct us to the most exalted type of animal existence. 



These different sections, which constitute, in fact, so many dis- 

 tinct classes into which the HETEROGANGLTATA have been divided 

 by zoologists, we shall now proceed to examine seriatim ; beginning, 

 as heretofore, with the most imperfectly organized, and gradually 

 tracing the developement of superior attributes and more exalted 

 faculties as the nervous centres attain greater magnitude and con- 

 centration. 



CHAPTER XIX. 



ClRRHOPOUA.* 



(389.) HOWEVER distinct in outward appearance, and even in 

 their internal economy, the creatures composing the primary divisions 

 of animated nature may seem to be when superficially examined, 

 closer investigation invariably reveals to the zoologist gradations of 

 structure connecting most dissimilar types of organization, and lead- 



* xtppof, a cirrus ; -rov;, -rolog, a foot. 



