FOREWORD TO TEACHERS 11 



big underlying biological concepts on which society is built, have 

 all been used to the end that the pupil will become a better, 

 stronger and more unselfish citizen. The " spiral ' or cyclic 

 method of treatment has been used throughout, the purpose being 

 to ultimately build up a number of well-rounded concepts by 

 constant repetition but with constantly varied viewpoint. 



The sincere thanks of the author is extended to all who have 

 helped make this book possible, and especially to the members 

 of the Department of Biology in the De Witt Clinton High School. 

 Most of the men there have directly or indirectly contributed 

 their time and ideas to help make this book worth more to teachers 

 and pupils. The following have read the manuscript in its entirety 

 and have offered much valuable constructive criticism : Dr. Herbert 

 E. Walter, Professor of Zoology in Brown University ; Miss Elsie 

 Kupfer, Head of the Department of Biology in Wadleigh High 

 School ; George C. Wood, of the Department of Biology in the 

 Boys' High School, Brooklyn ; Edgar A. Bedford, Head of Depart- 

 ment of Biology in the Stuyvesant High School ; George E. Hew- 

 itt, George T. Hastings, John D. McCarthy, and Frank M. Wheat, 

 all of the Department of Biology in the De Witt Clinton High 

 School. 



Thanks are due, also, to Professor E. B. Wilson, Professor G. N. 

 Calkins, Mr. William C. Barbour, Dr. John A. Sampson, W. C. 

 Stevens, and C. W. Beebe, Dr. Alvin Davison, and Dr. Frank 

 Overton; to the United States Department of Agriculture; the 

 New York Aquarium ; the Charity Organization Society ; and the 

 American Museum of Natural History, for permission to copy and 

 use certain photographs and cuts which have been found useful in 

 teaching. Dr. Charles H. Morse and Dr. Lucius J. Mason, of the 

 De Witt Clinton High School, prepared the hygiene outline in the 

 appendix. Frank M. Wheat and my former pupil, John W. Teitz, 

 now a teacher in the school, made many of the line drawings and 

 took several of the photographs of experiments prepared for this 

 book. To them especially I wish to express my thanks. 



At the end of each of the following chapters is a list of books 

 which have proved their use either as reference reading for students 

 or as aids to the teacher. Most of the books mentioned are within 



