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 Paleocar- 
dda. 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. 8. 
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, 
