Biological Terminology

Abstract

DR. BATHER (NATURE, August 18, p. 778) wishes me to explain my glaring truism, “Variation is the sole cause of non-inheritance: apart from variations, like exactly begets like when parent and child develop under like conditions” [of nurture]. But does it need explaining? As he says, and as I have insisted, variation is non-inheritance, and for that reason the truism is glaring. The words “the sole cause of” are really redundant, and were introduced merely to emphasise the fact that there is no other cause. My justification for framing the truism lies in the fact that that truth is more honoured in breach than in observance in biological discussions. I have already expressed myself much in the following terms, but some repetition seems necessary. Every character is a product of antecedent and exciting cause, of nature and nurture, of potentiality and stimulus, of power to develop and opportunity to develop. Since the multicellular individual is derived from a germ, he can inherit only through it. In the germ are none of the characters subsequently developed in the soma, but only powers to develop them. Therefore, strictly speaking, he inherits nothing but these powers, the sum of which is his nature, while the sum of the influences which cause change (or arrest it) is his nurture. By a colloquialism, which is pardonable since it confuses no one, we speak of a child inheriting his parent's eyes, or hair, and so on. If a child in response to similar nurture produces hair like his parent's, he has not varied in this respect; he has inherited; he is like his parent both by nature and through nurture. If he develops different hair in response to similar nurture, he has varied; to that extent he has not inherited. If owing merely to different nurture (e.g. injury) he produces different hair, or even none at all, he has inherited, but not reproduced.