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 ; and partly because the interpretation 

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

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

 fore be — ] 



THE PKINCIPLES OF BIOLOGY. 



Vol. I. 



Pakt I. The Data of Biology. — Including those general 

 truths of Physics and Chemistry with which rational Biology 

 must set out. 



II. The Inductions or 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. Moephological 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 



