VARIATION. 263 



altering the balance of forces to which it has been hitherto 

 subject ; by supplying it with different proportions of the 

 assimilable matters it requires, and taking away some of the 

 positive impediments to its growth which competing wild 

 plants before offered. An animal taken from woods or plains, 

 where it lived on wild food of its own procuring, and placed 

 under restraint, while artificially supplied with food not quite 

 like what it had before, is an animal subject to new outer ac- 

 tions, to which its inner actions must be re-adjusted. From 

 the general law of equilibration we found it to follow, thai 

 " the maintenance of such a moving equilibrium ' as an or- 

 ganism displays, " requires the habitual genesis of internal 

 forces corresponding in number, directions, and amounts, to 

 the external incident forces as many inner functions, 

 single or combined, as there are single or combined outer ae 

 tions to be met " (First Principles, 133) ; and more recently 

 ( 27), we have seen that Life itself is "the definite combin- 

 ation of heterogeneous changes, both simultaneous and suc- 

 cessive, in correspondence with external co-existences and 

 sequences." Necessarily, therefore, an organism exposed to a 

 permanent change in the arrangement of outer forces, must 

 undergo a permanent change in the arrangement of inner 

 forces. The old equilibrium must be destroyed ; and a ne\v 

 equilibrium must be established. There must be func- 

 tional perturbations, ending in a re-adjusted balance oi 

 functions. 



If, then, change of conditions is the only known cause by 

 which the original homogeneity of a species is destroyed ; 

 and if change of conditions can affect an organism only by 

 altering its functions ; it follows that alteration of func- 

 tions is the only known internal cause to which the com- 

 mencement of variation can be ascribed. That such minoi 

 functional changes as parents undergo from year to year, are 

 influential on the offspring, we have seen to be proved by 

 the greater unlikeness that exists between children born to 

 the 'same parents at different times, than exists between 



