THE 



PRINCIPLES OF BIOLOGY 



BY 



HERBERT SPENCER 



AUTHOR OF SOCIAL STATICS, EDUCATION, STUDY OF SOCIOLOGY, 



ESSAYS : SCIENTIFIC, POLITICAL, AND SPECULATIVE, 



FACTORS OF ORGANIC EVOLUTION, ETC. 



IN TWO VOLUMES 

 VOL. II 



NEW YORK 

 APPLETON AND COMPANY 



'W 



