PREFACE 5 



cussion of Comparative Zoology. The addition of a 

 chapter on " The Origin of Animal Species " will, it is 

 hoped, enable the student to understand the most im- 

 portant, at least, of zoological theories. A number of 

 new figures have been incorporated. An asterisk at 

 the head of a chapter indicates that the subject-matter 

 of the chapter may be illustrated by practical work, 

 for which directions will be found in the Appendix. 



Acknowledgments are due to Messrs. D. Appleton 

 and Company for permission to reproduce Figures 

 39(11) and 367 from Thomson's "Outlines of Zoology " ; 

 to the J. B. Lippincott Company for permission to 

 reproduce Figures 207, 208, 212, and 256 from Piersol's 

 " Normal Histology," and Figure 368 from Smith's 

 " Economic Entomology " ; to Messrs. W. B. Saunders 

 and Company for permission to reproduce Figure 203 

 from G. C. Huber's edition of Bohm and Davidoff's 

 "Text-book of Histology," and to Professor Alfred 

 Schaper of the University of Breslau, for permission to 

 reproduce Figure 211 from his edition of Stohr's "Text- 

 book of Histology." 



CHARLES WRIGHT DODGE. 

 UNIVERSITY OF ROCHESTER. 



