QL-4 







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- 



s^ guage and illustrations, yet going far enough to constitute 



v 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 



v is encyclopedic, it is unfit for a text-book. This is pre- 

 v <^ pared on the principle of "just enough, and no more." 



^ It aims to present clearly, and in a somewhat new form, 



k 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- 



