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.!7° 
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 
Spencer: Principles of Biology, Sixth edition; London, Will- 
jams and Norgate. 1898. Vol. I. Chap. IV, §66. P. 224—226. 
1Spencer: Ibid. Vol. I. Chap. VIII: Heredity, § 84. P. 319. 
