Vlll PREFACE 



Introduction to Zoology, Holmes' Biology of the Frog, Hux- 

 ley's Physiology, Lankester's Treatise on Zoology, Lull's 

 Organic Evolution, Packard's Textbook of Entomology, 

 Parker's The Elementary Nervous System, Parker and Has- 

 well's Textbook of Zoology, Parker and Parker's Practical 

 Zoology, Scott's The Theory of Evolution, Shipley and 

 McBride's Zoology, Verworn's General Physiology, Walter's 

 Genetics, and The Human Skeleton, Wiedersheim's Compar- 

 ative Anatomy of Vertebrates, Wilson's The Cell (The Mac- 

 millan Co.). To The Macmillan Company is also due the 

 author's appreciation of the liberal attitude which they have 

 assumed in all the arrangements attendant upon the pub- 

 lication of the book. 



L. L. WOODRUFF. 

 Yale University, 

 May, 1922. 



