366 NEW BOOKS, WITH SHORT NOTICES. KmS. jinTrS^ 
These title-headings are as follows : — On Classification in 
General; The Characters of the Classes of the Invertebrata ; 
The Characters of the Classes of the Vertebrata ; On the 
Arrangement of the Classes into Larger Groups ; The Sub- 
classes and Orders into which the Classes of the Vertebrata are 
divisible ; The Orders into which the Classes of the Invertebrata 
are divisible. The first chapter extends over no more than about 
five pages, and yet is a masterpiece in the simplicity of style in 
which it lays some difficult abstract considerations before the 
mind of the student. The aim, raison d'etre, and the general basis 
of the principles of classification, involve in their explanation 
considerable metaphysical difficulties ; and we know of no harder 
task than to have to expound these things to the young student. 
Nevertheless, we think Professor Huxley has done so in his hap- 
piest style, and we only wish we could reproduce this chapter 
in extenso. Eeferring to the mistake which some anatomists make 
of confounding the admission of a causal connection of natural 
phenomena with an affirmation of our knowledge of the nature of 
" that causal connection," Professor Huxley makes the following 
remarks, which we beg to quote in concluding our observations on 
this excellent book : — 
" Cuvier, the more servile of whose imitators are fond of citing 
his mistaken doctrines as to the nature of the methods of 
palaeontology against the conclusions of logic and of common 
sense, has put this so strongly that I cannot refrain from quoting 
his words : ' But I doubt if any one would have divined, if un- 
taught by observation, that all ruminants have the foot cleft, and 
that they alone have it. I doubt if any one would have divined 
that there are frontal horns only in this class ; that those among 
them which have sharp canines for the most part lack horns. 
However, since these relations are constant, they must have some 
sufficient cause ; but since we are ignorant of it, we must make 
good the defect of the theory by means of observation ; it enables 
us to establish empirical laws which become almost as certain as 
rational laws, when they rest on sufficiently repeated observations ; 
so that now whoso sees merely the print of a cleft hoof may con- 
clude that the animal which left this impression ruminated, and 
this conclusion is as certain as any other in physics or morals. 
This footprint alone, then, yields to him who observes it the form 
of the teeth, the form of the jaws, the form of the vertebrae, the 
form of all the bones of the legs, of the thighs, of the shoulders, 
and of the pelvis of the animal which has passed by : it is a surer 
mark than all those of Zadig.' " * 
* * Ossemens Fossiles :' ed. 4"«, t. l^', p. 184. 
