CHAPTER I. 

 PRELIMIKAEr. 



§ 109. In the foregoing Part, we have contemplated the 

 most important of the generalizations to which biologists 

 have been led by observation of organisms. These Induc- 

 tions of Biology have also been severally glanced at on their 

 deductive sides ; for the purpose of noting the harmony that 

 exists between them, and those primordial truths set forth in 

 First Principles. Having thus studied the leading pheno- 

 mena of life separately, we are prepared for studjdng them in 

 their ensemble, with the view of arriving at the most general 

 interpretation of them. 



There is an e7isenible of vital phenomena presented by each 

 organism in the course of its growth, development, and decay ; 

 and there is an enseinlle of vital phenomena presented by 

 the organic world as a whole. Neither of these can be 

 properly dealt with apart from the other. But the last of 

 them may be separately treated more conveniently than the 

 .first. What interpretation we put on the facts of structure 

 and function in each living body, depends entirely on our 

 conception of the mode in which living bodies in general 

 have originated. To form some conclusion respecting this 

 mode — a provisional if not a permanent conclusion — must 

 therefore be our first step. 



We have to choose between two hjipotheses — the hypo- 

 thesis of Special Creation and the hj^pothesis of Evolution. 



