256 THE INDUCTIONS OF BIOLOGY. 



when changed to A', must be changed in all its functions ; 

 then the offspring of A' cannot be the same as they would 

 have been had it retained the form A. It involves a denial 

 of the persistence of force to say that A may be changed 

 into A', and may yet beget offspring exactly like those it 

 would have begotten had it not been so changed. That the 

 change in the offspring must, other things equal, be in the 

 same direction as the change in the parent, we may dimly see 

 is implied by the fact, that the change propagated throughout 

 the parental system is a change towards a new state of 

 equilibrium — a change tending to bring the actions of all 

 organs, reproductive included, into harmony with these new 

 actions. Or, bringing the question to its ultimate and 

 simplest form, we may say that as, on the one hand, ph)'- 

 siological units vAW, because of their special polarities, build 

 themselves into an organism of a special structure ; so. on 

 the other hand, if the structure of this organism is modified 

 by modified function, it will impress some corresponding 

 modification on the structures and polarities of its units. The 

 units and the aggregate must act and re-act on each other. 

 The forces exercised by each unit on the aggregate and by 

 the aggregate on each unit, must ever tend towards a balance. 

 If nothing prevents, the units will mould the aggregate into 

 a form in equilibrium with their pre-existing polarities. If. 

 contrariwise, the aggregate is made by incident actions to 

 take a new form, its forces must tend to re-mould the units 

 into harmony with this new form. And to say that the 

 physiological units are in any degree so re- moulded as to bring 

 their polar forces towards equilibrium with the forces of the 

 modified aggregate, is to say that when separated in the 

 shape of reproductive centres, these units will tend to build 

 themselves up into an aggregate modified in the same di- 

 rection. 



