based on the principle of Cephalization.—Herbivores, 175 
indicative, each, of inferiority of grade. They are feeble in the 
ead, and have no use for the forehead in attack or defense; 
they are weak as to means of defense of any kind; they have a 
lax condition of the extremities; they have a more complete 
and regular series of teeth, but as a result of a more diffused 
state of the systemic force, or less systemic control, 
C. Strenians. 
_ The distinctions of the Sirenians have already been sufficiently 
indicated (p. 169). 
In conclusion, the writer may here state that he does not look 
upon the classification which has been presented, as in all points 
that to which beyond question the right application of the princi- 
ple of cephalization leads; but only as that which, as far as he 
now understands the facts and the principle, appears to him to 
be correct to nature : 
D. Dynamical considerations. 
On page 174, it is likewise shown that a relaxation of the parts 
in the extremities of the limbs is concurrent with a relaxing also 
of the elements of the jaws. : 
us the head and the limbs, parts alike circumferential, 
undergo analogous changes under similar conditions—the am- 
Plification in the head increasing from the basal portion of the 
skull toward the extremity of the jaws; and that in the limbs 
mcreasing from the body toward the extremities of these limbs. 
Now it is to be noted that, while the head and the limbs 
diminish in amplification toward their basal portions, they are 
Separated in the same species by a long-amplificate neck. It seems 
ollow, therefore, that the head is one centre of amplification, 
nd the bo y another; or, in other words, that there are two 
distinct centres of amplification, a cephalic and a thoracic, the 
former the prima 
tion, should be considered as subordinate to the cephalic, or to 
the thoracie, centre, or to both equally. In reply, it is to he 
that in the head. Moreover, short limbs and a short neck go 
together (as in the natatorial Herbivores and Mutilates), even 
