Spencer 225 



tion of inheritance and to the conceptions of inheritance 

 which have been formed. 



Spencer 



This author's idea of "physiological units/' inter- 

 mediate between the morphological units or cells and the 

 chemical units or molecules, and representing the last 

 irreducible vital elements, is well known. 170 



If one supposes that in each organism there exists 

 only a single variety of these units, Spencer believes the 

 explanation of the inheritance of acquired characters 

 would follow immediately from that. 



"Just as the physiological units 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 upon the struc- 

 ture and polarities of its units. The units and the 

 aggregate must act and react on each other. If nothing 

 prevents, the units will mould the aggregate into a form 

 which will be in equilibrium with their pre-existing polar- 

 ities. If contrariwise the aggregate is made by incident 

 actions to take a new form, its forces must tend to mould 

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

 that the physiological units are in any degree so 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 centers, these units 

 will tend to build themselves up into an aggregate mod- 

 ified in the same direction." 171 



170 Spencer: Principles of Biology, Sixth edition; London, Will- 

 iams and Norgate. 1898. Vol. I. Chap. IV, $66. P. 224226. 

 171 Spencer : Ibid. Vol. I. Chap. VIII : Heredity, $ 84. P. 319- 



