SYSTEM OF NATURE. 
133 
the position of those contents, inter se , I find I am pro¬ 
posing problems which the more I contemplate the more 
I feel the improbability of my ever being able to solve. 
Cams, who seems one of the most profound and original 
thinkers on these abstruse subjects, appears to consider that 
universal nature consists of two organized groups,— ani¬ 
mals and vegetables; two geological groups, — earth and 
water; and two atmospherical groups, — gas and vapour. 
Without pretending to appreciate this division, and con¬ 
sequently without assuming that I can enforce or defend 
it, still I must acknowledge that I consider it worthy of 
mature consideration, not only as comprehending all the 
forms of matter perceptible to our senses, but as excluding 
such speculative additions as time, space, light, heat and 
motion, which clearly do not fall within the compass of our 
enquiry. The existence of such groups as those enumerated 
by Cams, proves the existence of an aggregate group, of 
which these are the component parts: and as animals form 
a portion of that aggregate group, the disposition of its 
component parts may be in some measure predicated by 
a comparison with those of the animal kingdom, which, as 
we have seen, appear to be so many epitomes of the whole. 
Returning, therefore, to the animal kingdom, we find on 
our first attempt to analyse its contents, that the great di¬ 
chotomy or division into vertebrate and invertebrate, forces 
itself on our notice. The primary divisions of inverte¬ 
brate animals, the articulate, mollusk and radiate, may, 
perhaps, be of somewhat unequal value, but if contrasted 
with the vertebrate, this slight discrepancy among them 
sinks into nothing before the vast discrepancy between ver¬ 
tebrate and invertebrate. Again, it must be observed, that 
each of the invertebrate groups is double, and divisible into 
