8 THE PURPOSE AND PLAN OF THIS BOOK 



Proof has been read critically by three of my former pupils, J. W. 

 Tietz, P. T. Lacy, and J. W. Ingle. To all of the above my thanks 

 are due« 



Thanks are due, also, to Prof. E. B. Wilson, W. C. Stevens, and 

 C. W. Beebe, Dr. Alvin Davison, Dr. Prank Overton, Mr. Spencer, 

 of the New York Aquarium, the United States Department 

 of Agriculture, and the American Museum of Natural History, 

 for permission to copy and use certain cuts and photographs 

 which have been found useful in teaching. Prof. G. N. Calkins 

 of Columbia University kindly loaned the photograph of the 

 Amoeba reproduced on page 182. E. AY. Coryell and J. W. Tietz 

 made several of the photographs of experiments. The photograph 

 of the humming bird was used by permission of the Polmer and 

 Schwing Company, Kochester, N.Y. In particular I am under 

 obligation to my former coworker. Dr. C. A. King, for his exam- 

 ple of earnest and inspiring work, to Mr. W. P. Hay, Head of the 

 Department of Biology and Chemistry, in the Washington, D.C., 

 High Schools, for his helpful criticisms, and to Messrs. Sedgwick 

 and Wilson, whose General Biology is a monumental work in ele- 

 mentary biological teaching. 



