242 THE INDUCTIONS OF BIOLOGY. 



only to remodel the proximately-affected industries; it will 

 dwindle away again after a moderate period, if the need for 

 it disappears. Second, that a long period must be required 

 before the re-actions produced by an enlarged industry can 

 cause a re-construction of the whole society, and before the 

 countless re-distributions of capital and labour can again 

 reach a state of equilibrium. And third, that only when 

 such a new state of equilibrium is eventually reached, can the 

 adaptive modification become a permanent one. How, 



in animal organisms the like argument holds, need not be 

 pointed out. The reader will readily follow the parallel. 



That organic types should be comparatively stable, might 

 be anticipated on the hypothesis of Evolution. The structure 

 of any organism being a product of the almost infinite series 

 of actions and reactions to which ancestral organisms have 

 been exposed; any unusual actions and reactions brought to 

 bear on an individual, can have but an infinitesimal effect in 

 permanently changing the structure of thu organism as a 

 whole. The new set .of forces, compounded with all the an- 

 tecedent sets of forces, can but inappreciably modify that 

 moving equilibrium of functions which all these antecedent 

 sets of forces have established. Though there may result a 

 considerable perturbation of certain functions — a considerable 

 divergence from their ordinary rhythms — yet the general centre 

 of equilibrium cannot be sensibly changed. On the removal 

 of the perturbing cause the previous balance will be quickly 

 restored : the effect of the new forces being almost obliterated 

 by the enormous aggregate of forces which the previous 

 balance expresses. 



§ 71. As thus understood, the phenomena of adaptation 

 fall into harmony with first principles. The inference that 

 organic types are fixed, because the deviations frcm thv:m 

 which can be produced within assignable periods are relatively 

 small, and because, when a force producing deviation ceases, 

 there is a return to something like the original state ; proves to 



