iv PREFACE, 



of the order or class ; but these are placed after a description 

 of one or a few examples of the group to which they may 

 belong. The simplest, most elementary forms are first no- 

 ticed, beginning with the Protozoa and ending with the Ver- 

 tebrates. In working up from the simplest forms to those 

 more complex, it is believed that this is the more logical and 

 philosophical method, and that in this way the beginner in the 

 science can better appreciate the gradual unfolding of the lines 

 of animal forms which converge toward his own species, the 

 flower and synthesis of organic life. Still the learner is ad- 

 vised to begin his work by a study of the first part of Chap- 

 ter VIII., on Vertebrates, and to master, with a specimen in 

 hand, the description of the frog, in order that he may have 

 a standard of comparison, a point of departure, from which 

 to survey the lower forms. 



Particular attention has been given to the development of 

 animals, as this subject has been usually neglected in such 

 manuals. Some original matter is introduced into the book ; 

 a new classification of the Crustacea is proposed, the orders 

 being grouped into the subclasses Neocarida and Palceocar- 

 ida. Most of the anatomical descriptions and drawings 

 have been made expressly for this book, and here the author 

 wishes to acknowledge the essential aid rendered by Dr. C. S. 

 Minot, who has prepared the drawings and descriptions of 

 the fish, frog, snake, turtle, pigeon, and cat. 



In compiling the book, the author has freely used the 

 larger works of Gegenbaur, Huxley, Peters and Carus, Claus, 

 Rolleston, and others, whose works are enumerated at the 

 end of the volume, and in many cases he has paraphrased 

 or even adopted the author's language verbatim when it has 

 suited his purpose. Besides these general works many mon- 

 ographs and articles have been drawn upon. 



In order to secure a greater accuracy of statement, and to 

 render the work more authoritative as a manual of Zoology, 



