126 
SYSTEM OF NATURE. 
to predicate their propensities, their food, their economy; 
to arrange each in accordance with these results, and thus 
prepare himself for the question, whether these successive 
creations afford types or examples of many systems, or are 
but portions of one system, and that a system which has 
not yet passed away ? I have no hesitation in saying that 
the latter is the case. 
We have seen that the animals known to us in a living 
state are constructed on certain plans, the more marked of 
which have been termed vertebrate, radiate, mollusk and 
articulate ; but other plans have been noticed, and indeed 
have been supposed by some naturalists quite equal in 
importance to what may be termed the Cuvierian groups 
above enumerated. The number of primary divisions has 
been variously stated as two, three, four, five, six, seven 
and eight: all these groups are framed with a reference to 
natural characters.* Now among all the extinct animals 
there is but one family that is not directly referrible to one 
or other of these groups. With this single exception — I 
allude to the trilobites — every fragment finds its place in 
some well-marked division, the representatives of which 
are still in the full enjoyment of life and happiness. Gold- 
fuss and Latreille describe the trilobites as having been 
furnished with legs; and the latter, without any hesitation, 
constitutes an order of Crustacea purposely to receive 
them. This question of their possessing legs is one con¬ 
cerning which doubts have been entertained; but the con¬ 
clusion as to their place in the system seems to be perfectly 
* Perhaps excepting the numbers three and five: the advocates of 
these numbers are, as it were, “horsed on an idea,” and their divisions on 
this account scarcely deserve the same credit as the rest. 
