November 25, 1920] 



NATURE 



405 



Letters to the Editor. 



(Tte Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither j 

 can he undertake to return, or to correspond with I 

 the writers of, rejected manuscripts intended for | 

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Heredity. 



May I bring the following considerations before 

 readers of Nature interested in tlie study of heredity 

 and evolution? I daresay 1 am wrong, but 1 should 

 be glad to learn just how 1 am wrong. 



The multicellular individual springs from a germ- 

 cell. Presumably he inherits solely through that cell. 

 in the germ are none of the cnaracters which he 

 afterwards develops— limbs, scars, instincts, know- 

 ledge, and the like. These are characters not of a 

 cell, but of a cell-community — the soma. The germ 

 contains nothing but potentialities (powers, capacities, 

 diatheses, tendencies) for producing in its massed cell- 

 descendants these communal characters in response 

 to fitting influences (stimuli) — food, internal secre- 

 tions, heat, light, moisture, functional activity (use), 

 injury, and the like. Strictly speaking, therefore, 

 nothing is inherited save potentialities — powers to 

 develop in this way and that in respftnse to this 

 and that stimulus. Lacking the right influences, an 

 individual may not reproduce all that he inherits, 

 but he' can reproduce nothing that he did not inherit. 

 Reproduction is inheritance plus development. In 

 the case of variations development occurs without 

 inheritance; the individual does not then reproduce; 

 he merely produces. Such colloquialisms as "The 

 son has inherited his father's muscles " do no harm 

 so long as; the real truth be borne in mind ; but if 

 the truth be forgotten, endless loose thinking, con- 

 fusion, and futile discussion may result, and often 

 has resulted, as we shall see presently. Problems 

 toncerning potentialities are, of course, matters for 

 the student of heredity. Problems concerning rcpro- 

 <luction (as to what influences cause development) are 

 i.-qually, of course, matters not for the student of 

 heredity, but for the student of physiology. 



The sum of the potentialities in the germ whence 

 the individual springs is his nature ; the sum of the 

 influences which play on him and cause, or prevent, 

 or change his development is his nurture. Both 

 nature and nurture are necessary and equal factors 

 in the development of all characters. The query as 

 to whether nature or nurture is the stronger is akin 

 to a query as to whether the steam or the engine is 

 the more potent in moving the train. Nature and 

 nurture are never warring, but always co-operating, 

 factors. 



Individuals differ bv nature and by nurture. They 

 vary, and then their differenres are innate or germinal. 

 They are modified, and then their differences are 

 acquired or fomatir. Obviously, the words in italics 

 are used intelligibly when employed to describe like- 

 nesses .TTid differencfs between individuals. Thus we 

 know what is meant when we are fold that one man 

 is bv n.iturc or by nurture darker than another. But, 

 obviously again, they are used incorrectly and un- 

 infcllicitilv xvhen employed to describe likcnesAM and 

 diffrniK cs between rhararters. How, for example, 

 is n he.Kl more innate and germinal and less acquired 

 and somatic tbiin a scar? Can anyone tell us in 

 precise langu.ii;<'? The scar is as much founded on 

 germin.il polmfialify as is the head; the head is as 

 much a product of nurture and as much situated in 

 . the soma an is the srar. K\-<ilution has so fashioned 

 the race whence the individ'i.il sprang (has conferred 



NO. 2665, VOL. 106] 



on it such a nature) that, given a certain kind of 

 nurture, he produces a head, and given another kind 

 of nurture, he produces a scar. Plainly, all characters 

 ;ire both innate and acquired, germinal and somatic, 

 in precisely the same sense and degree. Plainly, also, 

 inheritance (e.g. of latent ancestral traits) is one 

 thing, while reproduction is another and quite a 

 different thing. 



Of course, we may, if we please, give arbitrary, 

 limited, unusual meanings to our words. But we 

 shall then, with the multiplicity of meanings, risk 

 confused thinking. As Bacon said, "Men beheve 

 that their reason rules over words; but it is also the 

 case that words react, and in their turn use their 

 influence on the intellect." Thus we may limit the 

 terms "acquired " and "somatic" to those cfiaracters 

 which develop in response to use and injury, while 

 reserving the terms "innate" and "germinal" for 

 all other characters. This, indeed, is commonly 

 done. Thus the abnormal musculature of the black- 

 smith is termed "acquired," while the normal 

 development of the ordinary man is supposed to be 

 innate. But the result is confusion worse confoundcnl, 

 for tfie muscles of the ordinary man also develop 

 from birth forwards in response to use. Like most 

 human structures, unused muscles, oven in child- 

 hood, do not develop; they atrophy; they owe not 

 only their development, but even their maintenance 

 to use. If, then, we give these meanings to our 

 words, we must apply the term "acquire<l " to vastly 

 more than we do now, and we must go back to the 

 infant, or beyond him, to find the natural man. Or, 

 again, the word " innate " may be limited to the- 

 "normal," and "acquired " to the "uncommon." Irr 

 that case we should have to term variations " acquire- 

 ments," and call the English language germinal in 

 England and acquired in France. In fact, no matter 

 what arbitrary meanings we take, the moment we 

 embark on them we are swamped in a sea of con- 

 fusion. 



Darwin founded his theory of natural sel<"cfion on 

 the supposition that innate likenesses and differences 

 between individuals were transmissible. However he 

 expressed himself at times, his meaning was usually 

 clear. Lamarck founded his theorv on the supposi- 

 tion that acquired likenesses and differences between 

 individuals were transmissible ; but he expressed 

 himself in terms of characters, and his meaning, 

 as we shall see immediately, was never clear. 

 Gradually, especially after the advent of Weismaiin, 

 discussion centred more and more on characters, 

 some of which were termed "germinal" and others 

 "somatic." .\t present most biologists hold that 

 "acquire<l characters are not transmissible." But 

 here again, can anyone explain precisely what he 

 means? So far as I am able to judge, that pro- 

 nouncement is neither true nor untrue; It is purely 

 nonsensical. 



Consider the following, which I think most bio- 

 logists will consider true, and, I suppose, all will 

 consider intelligible : " Heads, being germinal charac- 

 ters, are inheritable; but scars, being somatic, not 

 germinal, are not inheritable." But since only 

 potentialities are present in the germ, all we can 

 mean by the statement that heads are transmissible 

 is that offspring, inheriting like natures from their 

 progenitors, reproduce, under liki- conditions, like 

 heads. If we gave our words the same' meanings, 

 wc should sav that a scar is inherited when a child 

 reproduces it under the same condition* as the parent 

 did (i.e. in response to the nurture of injury). The 

 child would then Ik" like, both bv nature and by 

 nurture, to the parent. But no biologist regards a 

 scar so reproduced as inherited. It would he 

 regarded as inherited only if I'l. ''■ i.nroducrd it 



