CATEGORIES OF CLASSIFICATION. 33 
wherever such a tendency is perceptible in the 
Radiates it is subordinate to the typical plan on 
which the whole group is founded. They are 
spheroidal bodies; yet, though many of them 
remind us of a sphere, they are by no means 
to be compared to a mathematical sphere, but 
rather to an organic sphere, so loaded with life, 
as it were, as to produce an infinite variety of 
radiate symmetry. The mathematical sphere 
has a centre to which every point of the sur- 
face bears identical relations ; such spheres do 
not exist in the Animal Kingdom. A sphere 
of revolution, in consequence of its rotation up- 
on its axis, presents equally flattened poles with 
meridians of equal value; this also is no organic 
character. A living sphere has unequal poles 
as well as unequal meridians, however much it 
may resemble a perfectly spheroidal body, and 
the whole organization is arranged, not neces- 
sarily around a centre, but always around a 
vertical axis, to which the parts bear equal re- 
lations. 
In Mollusks there is a longitudinal axis and 
a bilateral symmetry ; but the longitudinal 
axis in these soft concentrated bodies is not 
very prominent, except in the highest class ; 
and though the two ends of this axis are dis- 
tinct from each other, the difference is not so 
marked that we can say at once, for all of 
2% c 
