348 THE INDUCTIONS OF BIOLOGY. 



seen to be needful for producing the fertilized germs of new 

 individuals. And were not these individual differentiations 

 ever being mutually cancelled, they would end in a fatal 

 narrowness of adaptation. 



This truth will be most clearly seen if we reduce it to its 

 purely abstract form, thus: — Suppose a quite homogeneous 

 species, placed in quite homogeneous conditions ; and suppose 

 the constitutions of all its members in complete concord with 

 their absolutely-uniform and constant conditions ; what must 

 happen? The species, individually and collectively, is in a 

 state of perfect moving equilibrium. All disturbing forces 

 have been eliminated. There remains no force which can, in 

 any way, change the state of this moving equilibrium ; either 

 in the species as a whole or in its members. But we have 

 seen (First Principles ^ § 1*^3 ) that a moving equilibrium is 

 but a transition towards complete equilibration, or death. The 

 absence of differential or un-equilibrated forces among the 

 members of a species, is the absence of all forces which can 

 cause changes in the conditions of its members — is the ab- 

 sence of all forces which can initiate new organisms. To 

 say, as above, that complete molecular homogeneity existing 

 among the members of a species, must render impossible that 

 mutual molecular disturbance which constitutes fertilization, 

 is but another way of saying that the actions and re-actions 

 of each organism, being in perfect balance with the actions 

 and re-actions of the environment upon it, there remains in 

 each organism no force by which it differs from any other 

 — no force which any other does not meet with an equal 

 force — no force which can set up a new evolution among the 

 units of any other. 



And so we reach the remarkable conclusion that the life of 

 a species, like the life of an individual, is maintained by the 

 unequal and ever-varying actions of incident forces on its 

 different parts.* An individual homogeneous throughout, and 



* A propos of this sentence one of my critics writes : — " I cannot find in 

 this book the statement as first made that the ' life of an individual is main- 



