PREFACE TO THE FIRST EDITION. xv ii 



[In logical order should here come the application of these 

 First Principles to Inorganic Nature. But this great division 

 it is proposed to pass over : partly because, even without it, the 

 scheme is too extensive j and partly because the interpretation 

 of Organic Nature after the proposed method, is of more im- 

 mediate importance. The second work of the series will there- 

 fore be] 



THE PKINCIPLES OF BIOLOGY. 

 VOL. I. 



PART I. THE DATA OF BIOLOGY. Including those general 

 truths of Physics and Chemistry with which rational Biology 

 must set out. 



II. THE INDUCTIONS OF BIOLOGY. A statement of the 

 leading generalizations which Naturalists, Physiologists, and 

 Comparative Anatomists, have established. 



III. THE EVOLUTION OF LIFE. Concerning the specula- 

 tion commonly known as " The Development Hypothesis " 

 its a priori and a posteriori evidences. 



VOL. II. 



IV. MORPHOLOGICAL DEVELOPMENT. Pointing out the 

 relations that are everywhere traceable between organic forms 

 and the average of the various forces to which they are sub- 

 ject; and seeking in the cumulative effects of such forces a 

 theory of the forms. 



V. PHYSIOLOGICAL DEVELOPMENT. The progressive dif- 

 ferentiation of functions similarly traced; and similarly in- 

 terpreted as consequent upon the exposure of different parts 

 of organisms to different sets of conditions. 



VI. THE LAWS OF MULTIPLICATION. Generalizations re- 

 specting the rates of reproduction of the various classes of 

 plants and animals; followed by an attempt to show the de- 

 pendence of these variations upon certain necessary causes.* 



* The ideas to be developed in the second volume of the Principles of 

 Biology the writer has already briefly expressed in sundry Review- Arti- 

 cles. Part IV. will work out a doctrine suggested in a paper on " The 

 2 



