Now race and descent mean for him the same thing.

Hence a race-mark, if one is to be found, must stand for, by co-existing with, the whole mass of properties that form the inheritance.

Can colour serve for a race-mark in this profound sense?
That is the only question here.
First of all, what is the use of being coloured one way or the other?
Does it make any difference?
Is it something, like the heart-line of the hand, that may go along with useful qualities, but in itself seems to be a meaningless accident?
Well, as some unfortunate people will be able to tell you, colour is still a formidable handicap in the struggle for existence.

Not to consider the colour-prejudice in other aspects, there is no gainsaying the part it plays in sexual selection at this hour.

The lower animals appear to be guided in the choice of a mate by externals of a striking and obvious sort.