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 



N E W YORK 



D. APPLETON AND COMPANY 

 1806 



