352 DAJtWINIJJTJL 



ation of a force which till then was retained in a po- 

 tential state by some opposing force or obstacle, over- 

 coming which, it passes to a new equilibrium, and so 

 on. Hence alternations of dynamic activity and 

 static repose, of origination of species and types, al- 

 ternated with periods of stability or fixity. The time- 

 piece does not run down regularly, but " la force pro- 

 cede par saccades ; et . . . . par pulsations d'autant 

 plus energiques que la nature e"tait plus pres de son 

 commencement." 



Such is the hypothesis. For a theory of evolu- 

 tion, this is singularly unlike Darwin's in most re- 

 spects, and particularly in the kind of causes invoked 

 and speculations indulged in. But we are not here 

 to comment upon it beyond the particular point under 

 consideration, namely, its doctrine of the inherently 

 limited duration of species. This comes, it will be 

 noticed, as a deduction from the modern physical 

 doctrine of the equivalence of force. The reasoning 

 is ingenious, but, if we mistake not, fallacious. 



To call that " evolutive force " which produces the 

 change of one kind of plant or animal into another, is 

 simple and easy, but of little help by way of explana- 

 tion. To homologize it with physical force, as M. 

 Naudin's argument requires, is indeed a step, and a 

 hardy one; but it quite invalidates the argument. 

 For, if the " evolutive force " is a part of the physical 

 force of the universe, of which, as he reminds us, the 

 sum is fixed and the tendency is toward a stable equi- 

 librium in which all change is to end, then this evo- 

 lutive was derived from the physical force ; and why 

 not still derivable from it ? What is to prevent its 



