On the present state of Zoology. 27 
then, by combining- afterwards the results obtained separately in this 
manner, we may one day be in a position to form some judgment of 
the true natural system. But, before selecting- our particular field of 
observation, it is very desirable that we take, as far as possible, a ge- 
neral view of the whole subject. This is requisite, in order that we 
may get some idea of that uniformity of plan which pervades more 
or less the entire animal kingdom, and of that complicated chain of 
affinities by which its several divisions are held together. Hardly 
any group is circumscribed by such absolute boundaries, as to admit 
of being viewed correctly, except in connection with all others to 
which it bears any kind of relation. It may not be necessary to study 
these others in detail, but without some knowledge of them, we shall 
hardly prosecute successfully our own department. Except we have 
some acquaintance with other structures, we shall hardly set a right 
value upon those modifications of structure which come before us ; 
and except we see something of the affinities of other animals, we 
shall hardly arrange according to their true relations those with which 
we are concerned. We shall especially overlook those approaches to 
the organization of contiguous groups by which is effected a passage 
from one to another, and those partial resemblances, or relations of 
analogy, which may be so often (some think always) traced between 
corresponding parts of two parallel series. 
With respect to the particular groups, which, in the present state 
of the science, call most loudly for the attention of naturalists, we 
can only make a few remarks, supplementary to those which we have 
already made elsewhere.* We would observe, generally, that it is 
towards the bottom of the system that their exertions are most want- 
ed. We as yet know but little of the classification of the Invertebrate 
animals, below the Mollusca and Annulosa. We may think that we 
can, with some appearance of truth, point out the leading divisions, 
or even proceed to the arrangement of the more subordinate groups ; 
but every day is bringing to light some fresh discoveries calculated to 
make us mistrust those views which are founded more upon a priori 
reasoning than upon actual observation. We are so in ignorance of 
the real structure of certain families ; we find others established upon 
characters of general resemblance, but offering internally such diffe- 
rences of organization ; that we can hardly say at present, with re- 
ference to these animals, on what systems of organs we can most re- 
ly as the basis of a natural classification, or indeed, in many instances, 
what organs are present. It is a question of dispute at this moment, 
* Report on Zoology, p. 249. 
