MOLLUSC A. 
INVERTEBRAL ANIMALS 
Invertebral animals are those which are destitute of a spine, 
or back bone. This great division of animated beings possess 
few positive characters which they have in common. Some 
have their bodies protected by a shelly covering ; others have no 
other defence than a soft and tender skin ; while others have 
their members surrounded by crustaceous plates. The nervous 
and circulating systems are less perfect than in animals with a 
spine; and few of them have red blood. The spinal chord 
is represented in molluscous animals by ganglions of the nervous 
filaments. None of the invertebral animals possess all the 
senses ; and the sexes are frequently united in the same indi¬ 
vidual : while, in others, the species is continued by a process 
somewhat resembling vegetation. 
Cuvier arranges invertebral animals into three great divisions. 
1st, Those destitute of a skeleton, which are termed Mollusca. 
2d, Animals whose trunk is divided into rings, these are called 
Articulata. 3d, Those animals known by the name of Zoophytes, 
which Cuvier calls Radiata. 
DIVISION II.—MOLLUSCA. 
Class I. Mollusca 
II. CONCHIFERA 
Class III. Tunicata 
IV. ClIlRIPIDA 
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