) deduced therefrom will also be discrete and unconnected and therefore useless.

And that is what we find; for just in so far as Wohlgemuth and Wertheimer identify pure motion or the after-effect with ordinary motion, they construct their physiological theories to accommodate both; and in so far as Wohl- gemuth distinguishes motion from successive and continuous change of position 1 , he must be held to give a purely illusory theory of motion or he assumes the existence of what he calls a " subcortical centre of move- ment 2 ," and that, after all, is nothing but a ready made, specially created machine, which cannot have evolved out of the fundamental neural pro- cesses.

But surely both the body and the mind must evolve; and if so each must evolve out of its own fundamental processes by the inner necessity and illumination that is given by progressively increasing effectiveness.

To treat experience as a heterogeneous collection of elementary varie- ties, more or less similar, but essentially independent, therefore renders every scientific endeavour based upon the study of experience nugatory.

Experience, like the starry sky which guides the sailor, is not merely one of the happy accidents of creation, merely "just so," and no more.