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, 

 "are more easily made and more brilliant probably than observations; 

 but it is 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 the 

 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, is a 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. — Ed. 



f "The Ocean World," from the French of Louis Figuier. "The Insect 

 World," from the French of the same author. 



