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JOURNAL OF SCIENCE AND ARTS. 
[SECOND SERIES.} 
Arr. XIII.—The Classification of Animals based on the principle 
of Cephalization ; by James D. Dana.—No. III. Classification 
of Herbivores.’ 
THE principle of cephalization and its applications rest on the 
following simple facts : . 
( n animal is embodied or concentred force, which force 
manifests polarity in the results of its action in development, that 
is, in the oppositeness of the anterior and_ posterior extremities 
of the structures evolved and also in the dorso-ventral relations 
of these structures. 
... 2.) The primary potential centre is in the head, or more pre- 
cisely, in the cephalic nervous mass—an animal being funda- 
mentally cephalized organism. But, besides this, there may 
(4.) The differences just mentioned are expressed in the a 
ture of the organism; and all such expressions are necessarily 
expressions of grade. 
(6.) Each of these kinds of differences must have expression, 
or, be apparent, (a) through the various circumstances attending 
+ ad 
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