PLAN AND PURPOSE OF THIS BOOK 9 



The laboratory exercise immediately precedes the textbook 

 discussion, the latter being used to clear up any false inferences 

 the pupil may have made from the specimen in hand and to fix 

 the object of the problem in the mind of the pupil. Too often 

 has a laboratory exercise meant nothing to a pupil but " busy 

 work." A plainly outhned and organized plan of attack, a few 

 references to the text or to previous work performed, and a definite 

 problem will result in better and more definite laboratory work. 

 For use with this book a manual for the solution of laboratory 

 problems has been prepared by my coworker, Mr. R. W. Sharpe. 

 The problems to be solved with the aid of the manual are in 

 boldface italics. It is neither expected or desirable that a pupil 

 take all of the problems so indicated in a year's course. 



Two styles of type have been used in the text. The larger 

 tj-pe contains material which is believed to be of first impor- 

 tance, the smaller type the less important topics. The manuscript 

 was read in its entirety by Professor H. E. Walter of Brown 

 University'. To him I owe sincere thanks for many helpful 

 criticisms and suggestions. 



Acknowledgments are due to Miss A. P. Hazen, Head of the 

 Department of Biology in the Eastern District High School; 

 to H. G. Barber, E. A. Bedford, R. E. Call, John E. McCarthy, 

 C. F. Morse, and R. W. Sharpe of the De Witt Clinton High School; 

 Mr. C. W. Beebe, Curator of Birds, New York Zoological Park; 

 W. P. Hay, Head of the Department of Biology and Chemistry 

 of the Washington, D.C., High Schools; and Professor A. E. Hill 

 of New York University, for their careful reading and criticism 

 of parts or all of the proof. 



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

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

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

 ton; to the United States Department of Agriculture; the New 

 York Aquarium; the Charity Organization Society; the Folmer 

 and Schwing Company, Rochester, N.Y. ; and the American 

 Museum of Natural History, for permission to copy and use certain 

 photographs and cuts which have been found useful in teaching. 

 My acknowledgments are also due to Mr. A. C. Doane of the 

 Central High School, Grand Rapids, Mich., for permission to use 



