

SPENCER'S PHYSIOLOGICAL UNITS 401 



by reference to the way in which pieces of a Begonia-leaf will 

 reproduce the whole plant. " The assumption to which we 

 seem driven by the ensemble of the evidence, is that sperm- 

 cells and germ-cells [better, egg-cells] are essentially nothing , 

 more than vehicles, in which are contained small groups of the . 

 physiological units in a fit state for obeying their proclivity 

 towards the structural arrangement of the species they belong 

 to." If the likeness of offspring to parents is thus determined, 

 it becomes manifest, a priori, that besides the transmission of 

 generic and specific peculiarities, there will be a transmission of 

 those individual peculiarities which, arising without assignable 

 causes, are classed as " spontaneous." So far, in our quotations, 

 there is no distinct suggestion of the central idea of pangenesis 

 nor of the transmissibility of modifications. 



But Spencer goes on to say : " That changes of structure caused 

 by changes of action must also be transmitted, however obscurely, 

 from one generation to another, appears to be a deduction from 

 first principles or if not a specific deduction, still, a general 

 implication. 7 . . . The units and the aggregate must act and^ 

 react 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 remoulded 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 direction " (p. 256). 

 That is to say, representative physiological units of the body 

 congregate in vehicles which we call ova and spermatozoa, 

 carrying with them, on their journey to form a new generation, 



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