THE SCOPE OF BIOLOGY. 131 



aspects of the subject. Recognizing the general facts of 

 multiplication, without reference to their modes or immediate 

 causes, it concerns itself simply with the different rates of 

 multiplication in different kinds of organisms and different 

 individuals of the same kind. Generalizing the numerous 

 contrasts and variations of fertility, it seeks a rationale of 

 them in their relations to other organic phenomena. 



§ 42. Such appears to be the natural arrangement of 

 divisions and subdivisions which Biology presents. It is, 

 however, a classification of the parts of the science when fully 

 developed; rather than a classification of them as they now 

 stand. Some of the subdivisions above named have no recog- 

 nized existence, and some of the others are in quite rudi- 

 mentary states. It is impossible now to fill in, even in 

 the roughest way, more than a part of the outlines here 

 sketched. 



Our course of inquiry being thus in great measure deter- 

 mined by the present state of knowledge, we are compelled 

 to follow an order widely different from this ideal one. It 

 will be necessary first to give an account of those empirical 

 generalizations which naturalists and physiologists have 

 established: appending to those which admit of it, such de- 

 ductive interpretations as First Principles furnishes us with. 

 Having done this, we shall be the better prepared for dealing 

 with the leading truths of Biology in connexion with the 

 doctrine of Evolution. 



