THE CONVERGENCE OF THE EVIDENCES. 47 3 



173. But the conclusion deductively reached, in in har 

 mony with the inductive conclusion. Passing from the evi 

 dence that evolution has taken place, to the question How 

 has it taken place ? we find in known agencies and known 

 processes, adequate causes of its phenomena. 



In astronomic, geologic, arid meteorologic changes, ever in 

 progress, ever combining in new and more involved ways, 

 we have a set of inorganic factors to which all organisms are 

 exposed; and in the varying arid complicating actions of 

 organisms on one another, wo have a sot of organic factors 

 that alter with increasing rapidity. Thus, -peaking gener 

 ally, all members of the Earth s Flora and Fauna are con 

 tinually passing into new environments experience per 

 petual re-arrangements of external forces. 



Each organic aggregate, whether considered individually 

 or as a continuously-existing species, is modified afresh by 

 each fresh distribution of external forces. To its pre-exist 

 ing differentiations, new differentiations are ad/led ; arid thus 

 that lapse from a more homogeneous to a more heterogeneous 

 state, which would have a fixed limit were the circumstance 

 fixed, has its limit perpetually removed by the perpetual 

 change of the circumstances. Meanwhile, that growing com 

 plexity of structure thus produced, must, in the average of 

 cases, be accompanied by an increasing definitenefcs of fetruc- 

 ture ; sir.ce only those organisms can survive which subject 

 themselves to aggregates of forces that are not, in their ess-en- 

 *iaLs, greatly unlike those with which their structures cor 

 respond. Ar.d at the same time that progression is thu* 

 necessitated as a general re-suit ; yet, as change of structure 

 arises orJy where there is change in the distribution of force*, 

 it will not take place in or^nisms which el ode change 

 in the distribution of force*, by migration or otherwise. 



These mrjdincations upon modifications which rewlt in 

 evolution structurally considered, are the a/cwrrjp&wraei:t* 

 of those functional alterations continually required to re- 

 fcqirilibrate inner with outer actions. That moving *q*ii- 



