PREFACE. 
The distinctive character of this work consists in the 
treatment of the whole Animal Kingdom as a unit; in 
the comparative study of the development and variations 
of organs and their functions, from the simplest to the 
most complex state; in withholding Systematic Zoology 
until the student has mastered those structural affinities 
upon which true classification is founded; and in being 
fitted for High Schools and Mixed Schools by its lan¬ 
guage and illustrations, yet going far enough to constitute 
a complete grammar of the science for the undergraduate 
course of any College. , 
It is designed solely as a manual for instruction. It is- 
not a work of reference, nor a treatise. So far as a book 
is encyclopedic,, it is unfit for a text-book. This is pre¬ 
pared on the principle of “ just enough, and no more.” 
It aims to present clearly, and in a somewhat new form, 
the established facts and principles of Zoology. All the¬ 
oretical and debatable points, and every fact or statement, 
however valuable, which is not absolutely necessary to a 
clear and adequate conception of the leading principles, 
are omitted. It is written in the light of the most recent 
phase of the science, but not in the interest of any par¬ 
ticular theory. To have given an exhaustive survey of 
animal life would have been not only undesirable, but 
impossible. Even Cuvier’s great work must be supple- 
