DIRECT EQUILIBRATION. 521 



functions, and the various compound rhythms resulting from 

 their combinations, are so adjusted as to balance the actions 

 to which the organism is subject: there is a constant or 

 periodic genesis of energies which, in their kinds, amounts, 

 and directions, suffice to antagonize the energies the organism 

 has constantly or periodically to bear. If, then, there exists 

 this moving equilibrium among a set of internal actions, 

 exposed to a set of external actions, what must result if any 

 of the external actions are changed? Of course there is no 

 longer an equilibrium. Some energy which the organism 

 habitually generates, is too great or too small to balance some 

 incident energy; and there arises a residual energy exerted 

 by the environment on the organism, or by the organism on 

 the environment. This residual or unbalanced energy, of 

 necessity expends itself in producing some change of state in 

 the organism. Acting directly on some organ and modify- 

 ing its function, it indirectly modifies dependent functions 

 and remotely influences all the functions. As we have 

 already seen ( 68, 69), if this new energy is permanent, its 

 effects must be gradually diffused throughout the entire sys- 

 tem; until it has come to be equilibrated in producing those 

 structural rearrangements whence result a counter-balancing 

 energy. 



The bearing of this general truth on the question we are 

 now dealing with is obvious. Those modifications upon 

 modifications, which the unceasing mutations of their en- 

 vironments have been all along generating in organisms, 

 have been in each case modifications involved by the estab- 

 lishment of a new balance with the new combination of 

 actions. In every species throughout all geologic time, 

 there has been perpetually going on a rectification of the 

 equilibrium, which has been perpetually disturbed by the 

 alteration of its circumstances; and every further hetero- 

 geneity has been the addition of a structural change entailed 

 by a new equilibration, J;o the structural changes entailed by 

 previous equilibrations. There can be no other ultimate in- 



