4 REPTILES AND BIRDS. 
changes which have been brought about in the course of immeasur- 
able time by the operation of causes more or less similiar to those 
which are at work at the present day.” Domestication and other 
circumstances have no doubt produced alterations in the form of many 
animals ; but none from which this inference can be drawn, except 
in the imagination of ingenious men, who strain facts to support a 
preconceived hypothesis. In spite of the innumerable forms which _ 
the pigeon assumes by cross-breeding and domestication, it still 
remains a pigeon ; the dog is still a dog; and so with other animals. 
Nor does it seem necessary, or calculated to advance our know- 
ledge of natural history, to form theories which can only disturb our 
existing systems without supplying a better. Systems are necessary 
for the purpose of arrangement and identification; but it should 
never be forgotten that all classifications are artificial—a framework 
or cabinet, into the partitions of which many facts may be stowed 
away, carefully docketed for future use. “ Theories,” says Le Vaillant, 
‘care more easily made and more brilliant probably than observations; 
but it 1s by observation alone that science can be enriched.” A 
bountiful Creator appears to have adopted one general plan in the 
organisation of all the vertebrate creation ; and, in order to facilitate 
their study, naturalists have divided them into classes, orders, and 
genera, formed on the differences which exist in the structure of their 
vital functions. The advantages of this are obvious, but it does not 
fathom what is unfathomable, or explain what is inexplicable in the 
works of God.* 
In previous volumes of this seriest we have endeavoured to give 
the reader some general notions of the form, life, and manners of the 
branches of the animal kingdom known as Zoophytes, Mollusca, 
Articulata, and Pisces. We now continue the superior sub-kingdom 
(to which the fishes also belong) of the vertebrated animals, so called 
from the osseous skeleton which encircles their bodies, in which <he 
vertebral column, surmounted by its appendage the cranium, forms 
the principal part. 
The presence of a solid frame in this series of animals admits of 
their attaining a size which is denied to any of the others ; while their 
nervous system is also more developed. ‘There is, consequently, a 
more exquisite sensibility in them than in the classes whose history 
* This, however, isa subject upon which naturalists of the highest rank hold 
‘different opinions, many of those most highly qualified to form a correct judgment 
advocating the tenets propounded by Mr. Charles Darwin. — Ep. . 
t+ ‘The Ocean World,” from the French of Louis Figuier. ‘‘ The Insect 
World,” from the French of the same author. 
yor 
