AMERICAN SCIENCE SERIES 



AN INTRODUCTION 



GENERAL BIOLOGY 



BY 



WILLIAM T. SEDGWICK, PH.D. 



Professor of Biology in the Massachusetts Institute of Technology, Boston 

 AND 



EDMUND B. WILSON, PH.D. 



Professor of Zoology in Columbia College, New York 



SECOND EDITION, REVISED AND ENLARGED 



47139 



NEW YORK 

 HENRY HOLT AND COMPANY 



^636 7 l8 " 



