CEPHALOPODES. 
337 
and incapable of active exertion, they maintain themselves amid living beings princi- 
pally by their fecundity, and the tenacity with which they retain life. 
DIVISION OF THE MOLLUSCA 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 
elongated productions, by means of which the animals progress, and seize upon objects. 
We call these the Cephalopodes. 
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 Pteropodes. 
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 
Gasteropodes. 
A fourth class is composed of those Mollusca in which the mouth lies concealed in 
the base of the cloak, which also incloses tl^.e branchiae 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 cilise of the same 
nature. We have called these the Brachiopodes. 
Lastly, there are some which, alike the other Mollusca in the cloak, the branchiae, 
&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 Cirrhopodes. 
THE FIRST CLASS OF MOLLUSCA. 
THE CEPHALOPODES.* 
The cloak unites under the body, and forms a muscular sac, that incloses ail the 
viscera. In several species, its sides are extended into fleshy fins. The head issues 
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 surface is armed with suckers, the 
animals fix themselves, by their means, with great force to whatever objects they em- 
brace. With their feet they seize their prey, walk, and swim. They swim with the 
head backwards, and crawl in all directions, with the head beneath and the body above. 
* For the name Mollusca, M. de Blainville proposes to substitute I classes is entirely my own, as well as the greater number of the sub- 
Mnlacozoa ; and he separates from them the Chitons and the Cirrho- I divisions to the second degree, 
pods, with which he makes a subtypical section nnder the name I t The Cephalophora of De Blainville. 
Malentozoaria. The following distribution of the Mollusca into | 
Z 
