Let it not be forgotten, however, that individual plasticity plays its part too in the determination of human colour.  The Anglo-Indian planter is apt to return from a long sojourn in the East with his skin charged with a dark pigment which no amount of Pears’ soap will remove during the rest of his life.  It would be interesting to conduct experiments, on the lines of those of Professor Boas already mentioned, with the object of discovering in what degree the same capacity for amassing protective pigment declares itself in children of European parentage born in the tropics or transplanted thither during infancy.  Correspondingly, the tendency of dark stocks to bleach in cold countries needs to be studied.  In the background, too, lurks the question whether such effects of individual plasticity can be transmitted to offspring, and become part of the inheritance.

One more remark upon the subject of colour.  Now-a-days civilized peoples, as well as many of the ruder races that the former govern, wear clothes.  In other words they have dodged the sun, by developing, with the aid of mind, a complex society that includes the makers of white drill suits and solar helmets.  But, under such conditions, the colour of one’s skin becomes more or less of a luxury.  Protective pigment, at any rate now-a-days, counts for little as compared with capacity for social service.  Colour, in short, is rapidly losing its vital function.  Will it therefore tend to disappear?  In the long run, it would seem—­perhaps only in the very long run—­it will become dissociated from that general fitness to survive under particular climatic conditions of which it was once the innate mark.  Be this as it may, race-prejudice, that is so largely founded on sheer considerations of colour, is bound to decay, if and when the races of darker colour succeed in displaying, on the average, such qualities of mind as will enable them to compete with the whites on equal terms, in a world which is coming more and more to include all climates.

* * * * *

Thus we are led on to discuss race in its mental aspect.  Here, more than ever, we are all at sea, for want of a proper criterion.  What is to be the test of mind?  Indeed, mind and plasticity are almost the same thing.  Race, therefore, as being the stiffening in the evolution of life, might seem by its very nature opposed to mind as a limiting or obstructing force.  Are we, then, going to return to the old pre-scientific notion of soul as something alien to body, and thereby simply clogged, thwarted and dragged down?  That would never do.  Body and soul are, for the working purposes of science, to be conceived as in perfect accord, as co-helpers in the work of life, and as such subject to a common development.  Heredity, then, must be assumed to apply to both equally.  In proportion as there is plastic mind there will be plastic body.