•PHYSIOLOGICAL UNITS' 91 



being roused into activity, as this or that accident may require ; 

 while as regards plants he is compelled to assume that " cells must 

 be distributed over the whole surface of the plant, each of which 

 can in certain circumstances become the starting point of a bud. 

 That is to say, each must contain, in a latent state the complete germ- 

 plasm which is necessary for the production of an entire plant." 

 The way in which all these vast assortments of determinants would 

 need to be distributed for possible use, in addition to all those 

 which are required by Weismann's theories for actual use, afford 

 problems quite bewildering in their complexity. 



Let us turn now to an opposite and much simpler mode of 

 accounting for all these facts concerning budding, regeneration and 

 repair which was published by Herbert Spencer in his "Principles 

 of Biology " so long ago as 1863 ; and which, twelve years ago, was 

 still maintained by him in a celebrated controversy with Weismann 

 himself in the pages of " The Contemporary Review " for 1893-4. 



After referring to some of the facts concerning ' regeneration ' 

 known at the time, H. Spencer says : — "We must infer that a plant 

 or animal of any species is made up of special units, in all of 

 which there dwells the intrinsic aptitude ta aggregate into the 

 form of that species : just as in the atoms of a salt there dwells 

 the intrinsic aptitude to crystallise in a particular way. It 

 seems difficult to conceive that this can be so ; but we see that 

 it is so. Groups of units taken from an organism (providing they 

 are of a certain bulk and not much differentiated into special 

 structures) have this power of rearranging themselves ; and we are 

 thus compelled to recognise the tendency to assume the specific 

 form as inherent in all parts of the organism. Manifestly too, if we 

 are thus to interpret the reproduction of the organism from 

 one of its amorphous fragments, we must thus interpret the 

 reproduction of any minor portion of an organism by the 

 remainder ... In the one case as in the other, the vitalised 

 molecules composing the tissues show their proclivity towards a 

 particular arrangement ; and whether such proclivity is exhibited 

 in reproducing the entire form, or in completing it when rendered 

 imperfect, matters not." 



He then goes on to say : — " For this property there is no fit 

 term. If we accept the word polarity as a name for the force by 

 which inorganic units are aggregated into a form peculiar to them, 

 we may apply this name to the analogous force displayed by 



