554 Classification of Animals. 
3. The contents of such a circular group are symbolically (or 
analogically) represented by the contents of all other circles in the 
animal kingdom. 
4. That these primary divisions of every group are characte- 
rized by definite peculiarities of form, structure, and economy, 
which, under diversified modifications, are uniform throughout the 
animal kingdom, and are therefore to be regarded as the primary 
types of nature. 
5. That the different ranks or degrees of circular groups ex- 
hibited in the animal kingdom are nine in number, each being in- 
volved within the other. 
These he proceeds to establish by interesting details, and which, 
so far as we have had an opportunity of examining, tend to sub- 
stantiate their truth and universality as general laws. In regard 
to the first, it is almost unnecessary to say we have long considered 
it as fully established, not only by the arguments advanced by its 
discoverer, but by the subsequent severe analytical examination it 
has undergone. As to the second proposition, it is, we believe, likely 
to prove correct, being in accordance with the first division of na- 
tural bodies, animals, vegetables, and minerals, but we think a fur- 
ther investigation, particularly of the lower tribes of animals, is re- 
quired, before it can be fully established as a general law. Should, 
however, the three divisions of the aberrant group be found inva- 
riably to form a circle of their own, then we must consider them 
only as one, though always divisible, or made up of three secondary 
circles, representing the Rasorial, Grallatorial, and Natatorial 
types; this law, however, of an actual trinary, instead of a quinary 
disposition, does not affect the natural series by which they are 
united; for, as Mr Swainson justly observes, "the discovery of 
the union of Mr M'Leay's three aberrant groups into a circle of 
their own is the addition only of a new property superadded to 
that which they were known to possess, this property consisting of 
uniting into a circle of themselves, as well as passing into the typi- 
cal and subtypical groups." The third proposition, on the law of 
representation, which there is every reason to believe is of universal 
and not of partial application, is ably treated, and only requires to 
be further tested and investigated in the lower departments of 
zoology, to be admitted as another general law. In the suc- 
ceeding chapter he enters into a detailed exposition of the fourth 
proposition, in which the primary types are pointed out. The 
fifth and last proposition is rested upon facts and observations, 
