THE PRINCIPLES 



BIOLOGY. 



BY 



HERBERT SPENCER, 



OF "THE PRINCIPLES OF PSYCHOLOGY," "ILLUSTRATIONS or PROGRESS,** 

 41 ESSAYS : MORAL, POLITICAL, AND ESTHETIC," " FIRST PRINCIPLES," 



"SOCIAL STATICS," "EDUCATION," ETC. 



VOL. L 



NEW YORE: 

 D. APPLETON AND COMPANY, 



1, 3, AND 5 BOND STREET. 



1886. 



