vi 



PREFACE. 



with a less expenditure of force than would be possible 

 under any other arrangement ; so that any alteration 

 would be a positive disadvantage to the animal. If, as 

 I consider probable, this fact should prove to be 01 

 much wider occurrence in Nature than these instances 

 show, it may serve to give us some slight glimpse oi 

 the mechanism by which the conservation of species 

 in Nature is secured. In Astronomy, the conserva- 

 tion of the Solar System depends upon certain well- 

 known conditions regulating the motions of the 

 several bodies of which that system consists ; and it 

 is a matter of indifference whether these conditions 

 were directly imposed by the Will of the Divine Con- 

 triver, or were the indirect result of some former con- 

 dition of the System. In either case, these conditions 

 are equally the foreseen result of the Contrivance. 

 If the present state of the Solar System be the result, 

 according to fixed laws, of some pre-existing state o* 

 that System, it may be said, in the language of Na- 

 turalists, to have been evolved out of its former state, 

 but in such an Evolution there was nothing left to 

 Chance ; it was all foreseen, and the Evolution itseL 

 presided over by the Divine Mind that planned the 

 whole. I cannot see why there may not be in Or- 

 ganic Life a similar process of Evolution of higher 

 from lower forms of existence ; but it is a Teleologi- 

 cal Evolution, in which every step and every result 

 was foreseen and planned beforehand. The Laws of 

 such an Evolution appear to me, in the present state 

 of our knowledge, to be entirely unknown. 



