Enough about heredity as a condition of evolution.  We return, with a better chance of distinguishing them, to the consideration of the special effects that it brings about.  It was said just now that heredity is the stiffening in human nature, a stiffening bound up with a more or less considerable offset of plasticity.  Now clearly it is in some sense true that the child’s whole nature, its modicum of plasticity included, is handed on from its parents.  Our business in this chapter, however, is on the whole to put out of our thoughts this plastic side of the inherited life-force.  The more or less rigid, definite, systematized characters—­these form the hereditary factor, the race.  Now none of these are ever quite fixed.  A certain measure of plasticity has to be counted in as part of their very nature.  Even in the bee, with its highly definite instincts, there is a certain flexibility bound up with each of these; so that, for instance, the inborn faculty of building up the comb regularly is modified if the hive happens to be of an awkward shape.  Yet, as compared with what remains over, the characters that we are able to distinguish as racial must show fixity.  Unfortunately, habits show fixity too.  Yet habits belong to the plastic side of our nature; for, in forming a habit, we are plastic at the start, though hardly so once we have let ourselves go.  Habits, then, must be discounted in our search for the hereditary bias in our lives.  It is no use trying to disguise the difficulties attending an inquiry into race.

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These difficulties notwithstanding, in the rest of this chapter let us consider a few of what are usually taken to be racial features of man.  As before, the treatment must be illustrative; we cannot work through the list.  Further, we must be content with a very rough division into bodily and mental features.  Just at this point we shall find it very hard to say what is to be reckoned bodily and what mental.  Leaving these niceties to the philosophers, however, let us go ahead as best we can.

Oh for an external race-mark about which there could be no mistake!  That has always been a dream of the anthropologist; but it is a dream that shows no signs of coming true.  All sorts of tests of this kind have been suggested.  Cranium, cranial sutures, frontal process, nasal bones, eye, chin, jaws, wisdom teeth, hair, humerus, pelvis, the heart-line across the hand, calf, tibia, heel, colour, and even smell—­all these external signs, as well as many more, have been thought, separately or together, to afford the crucial test of a man’s pedigree.  Clearly I cannot here cross-examine the entire crowd of claimants, were I even competent to do so.  I shall, therefore, say a few words about two, and two only, namely, head-form and colour.