398 LAWS OF MULTIPLICATION. 



in excess, had nothing to prevent them from remaining in 

 excess, the race would disappear ; and clearly if the forces 

 preservative of race, when once in excess, had nothing to 

 prevent them from remaining in excess, the race would go on 

 increasing to infinity. In the absence of any compensating 

 actions, the onh^ possible avoidance of these opposite extremes 

 would be an unstable equilibrium between the conflicting 

 forces, resulting in a perfectly constant number of the species: 

 a state which we know does not exist, and against the 

 existence of which the probabilities are, as already said, 

 infinite. It follows, then, that as in every continuously- 

 existing species, neither of the two conflicting sets of forces 

 remains permanently in excess ; there must be some way of 

 stopping that excess of the one or the other which is ever 

 occurring. 



How is this done ? Should any one allege, in conformity 

 with the old method of interpretation, that there is in each 

 case a providential interposition to rectify the disturbed 

 balance, he commits himself to the supposition that of the 

 millions of species inhabiting the Earth, each one is yearly 

 regulated in its degree of fertility by a miracle ; since in no 

 two years do the forces which foster, or the forces which 

 check, each species, remain the same ; and therefore, in no 

 two years is there required the same fertility to balance 

 the mortality. Few if any will say that God continually 

 alters the reproductive activity of every parasitic fungus and 

 every Tape-worm or Trichina, so as to prevent its extinction 

 or undue multiplication ; which they must say if the}^ adopt 

 the hypothesis of a supernatural adjustment. And in the 

 absence of this hypothesis there remains only one other. 

 The alternative possibility is, that the balance of the pre- 

 servative and destructive forces is self-sustaining — is of the 

 kind distinguished as a stable equilibrium : an equilibrium 

 such that any excess of one of the forces at work, itself 

 generates, by the deviation it produces, certain counter- forces 

 that eventuall}' out-balance it, and initiate an opposite devia- 



