CLPIIALOPODES. 337 



and incapable of active exertion, they maintain themselves amid living beings princi- 

 pally by tneir fecundity, and the tenacity with which they retain life. 



DIVISION Of Till: Mol.UsCA INTO SIX CLASSES.* 



The general form of the body of the Mollusca being, in a sufficient degree, propor- 

 tional to the complication of their internal organization, indicates their natural divisions. 



In some, the body has the form of a sac, inclosing the branchiae, and open above, 

 whence there protrudes a head well developed, and crowned with certain strong fleshy 

 ( longated productions, by means of which the animals progress, and seize upon obje. 

 We call these the C'kpiialopodks. 



In others, the body is not open ; the head has no appendages, or only very minute 

 ones; the principal organs of locomotion are two wings, or membranous fins, placed 

 on the sides of the neck, and in which the branchial tissue is often spread. These are 

 the Ptekopodes. 



Others, again, crawl on the belly on a fleshy disk, sometimes, though rarely, com- 

 pressed into a fin. They have almost all a distinct head. We call these the 

 - Gasteiiopodes. 



A fourth class is composed of those Mollusca in which the mouth lies concealed in 

 the base of the cloak, which also incloses the branchia? and the viscera, and opens 

 either throughout its whole length, or at both its extremities, or at one only. These 

 are our Acephales. 



A fifth comprehends the species which, inclosed also in a cloak, and without an 

 apparent head, have fleshy or membranous arms, garnished with cilia? of the same 

 nature. We have called these the Bhacuiopodes. 



Lastly, there are some which, alike the other Mollusca in the cloak, the branchia?, 

 &c, differ from them in having numerous horny articulated members, and in a nervous 

 system more allied to that of the Annulose Animals. Of these we constitute our last 

 class, the C'jkiuiopodes. 



THE FIRST CLASS OF MOLLUSCA. 



THE CEPHALOPODES* 



The cloak unites under the body, and forms a muscular sac, that incloses all the 

 viscera, In several species, its sides are extended into fleshy fins. The head il 

 from the opening of the sac : it is roundish, furnished with two large eyes, and crowned 

 with fleshy conical arms or feet, varying in their length, and capable of being bent 

 very vigorously in every direction ; and, as their Burface is armed with suckers, the 

 animals fix themselvt b, bj their means, with great force to w batev< r objects they i m- 

 With their feet they seize- their prey, walk, and swim. They swim with the 

 leael backwards, and crawl in all directions, with the head beneath and the- body above. 



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