14 Psychophysical Evolution 



of them. For in psychology, as in biology, the race 

 series is but a continuous line of individual generations, 

 and to ask the question of the race is but to ask whether 

 parallelism holds for any given number of generations 

 of individuals wherever chosen in the line of descent — 

 this provided we admit that descent is by some form of 

 continuous hereditary transmission. 



The questions which arise about heredity, however, do not 

 trouble us, seeing that they are not within the domain of 

 strictly psychophysical inquiry, except in so far as our 

 theory must explain the inheritance of both physical and 

 mental characters to the same degree. For example, the 

 question of the ' continuity of germ plasm ' may be de- 

 cided one way or the other — either for or against the 

 actual continuous transmission of an identical substance — 

 without raising the question of a corresponding transmis- 

 sion of anything psychological. For if there be breaks in 

 the psychological series at those nodal points at which gener- 

 ation succeeds generation, there are also, by the principle of 

 equal continuity, discussed above, breaks also in the psycho- 

 physical, and we may find the psychological series beginning 

 again at the appropriate point in the development of the 

 organism of the new generation — the point at which the 

 psychophysical again begins. In other words, the advantage 

 gained from the psychophysical point of view is that if there 

 be apparent gaps in one of the series, we may either as- 

 sume them filled up by theoretical parallehsm with the other 

 series at these points, at which it has no gaps, or we may 

 — if we deny continuity to either — make gaps in the 

 second series in correspondence with the gaps found in 

 the first. We have in any given case, in short, either a 

 psychophysical fact, or we have not : if we have, then 



