SPECIAL ARTICLE. THE INHERITANCE OF ACQUIRED CHARACTERS.

Press, Volume LXVIII, Issue 20630, 20 August 1932, Page 14

SPECIAL ARTICLE. THE INHERITANCE OF ACQUIRED CHARACTERS.

The problem of the inheritance of acquired characters and habits has created more general interest and bitterer controversy than any other scientific problem, not only among scientists but at large. This is not at all surprising. In its ramifications it penetrates our activities and thoughts, from the commonplace pursuits of overy-day life to our convictions in education, science, and philosophy. The problem in short is this. Everybody knows that living organisms teact to external influences, structurally, organically, and in their instincts. Now, are modifications, induced by external agents, passed on to their progeny? Are they inherited? A few examples may serve as illustrations :

By special care a farmer has reared a fowl, a pig, or a cow of outstanding performance, yielding higher returns than is usual in the breed. Will the improvement be passed on to following generations, reared under ordinary farming conditions? Are exceptionally large wheat-ears, picked from a good spot in a field crop, likely to reproduce their unusual size when their grain in turn is sown on average land f By means of open-air schools, sports and games, tramping, sun-treatment, etc., we attempt to improve " the race " fundamentally. Are we likely to be successful? And, ultimately, are we to assume that the evolution of living organisms has been, is, and will be, a sequence of adaptations of acquisitions of characters and habits formed by external influences ? It is in the nature of life that we should strongly desire to answer these questions in ths affirmative. The very shortness of our individual lives impels U3 to strive for perpetuation, for a mark of our havingbeen; to leave things and beings in our ccxe better than we found them—permanently better. But how could we improve them lastingly if their improvements were not passed on? There would be no full satisfaction in husbandry, in education, in eugenics, if effort were to be lost with the death of the individual. ; This natural bias towards our believing in the inheritance of acquired characters is probably the strongest reason wfjy the belief persists, in spite of overwhelming evidence against it, collected in the course of the last half century.

Failure of All Experiments. The truth or falsity of the principle cannot be decided by speculation. It cannot even be decided by studying the series of extinct organisms found in successive layers of the earth. These series are admirable proof of the fact of evolution; but they are of no value in an attempt to discover the mechanism, the means and ways of evolution. The only reliable test is experiment under controlled conditions. Many of these Experiments have been carried out during the last thirty or forty years, and, to summarise their results, it can be stated that not one of them was able to prove inheritance of acquired characters. "Working with a pure line of beans, Johanti3en selected in several successive generations the largest and the smallest beans and compared their progenies. These were identical. The acquired" character, "size of seed," was not inherited. Similar experiments were conducted with many plants and animals. There is a variety of the Chinese primula, which bears under ordinary conditions, i.e., at a temperature of 50-60 degrees F., red flowers. Plants of this variety

transferred to a hot-house with, a temperature of 90 degrees P. form white flowers. Seedlings raided from these "white" hot-house plants, however, will bear red flowers when kept again at low temperatures. The acquired character, "white flower," again is not inherited. Nearly every year farmers send in wheat-ears of an unusual size to the Wheat Research Institute. These ears usually are picked out from an outstanding crop or part of a crop. When their seed is grown the following year beside a commercial sample of the same variety, invariably no .difference can be detected. Here again, the acquired character, "largo ear," or "large plant," induced by particularly favourable conditions of growth, is not inherited. It was further found that amputation or disiftse of certain organs for a number of generations—some experiments extended over more than 100 generations^—made no impression upon the formation of these organs in the progeny. That alterations in the life conditions of animals may cause changes of habit, but that these changed habits are not passed on to the progeny if the original conditions are restored, has been proved in many experiments. The fruit-fry, Drosopliila Melanogasta, has a general tendency to fly towards light. A pure strain of this fly was bred in complete darkness for sixty-nine generations, without the slightest effect on its habits. As soon as it was restored to light in the interior of a dark tube illuminated on one end, the vast majority of flies according to the original habit, flew towards the light.

Confusing Factors. In some experiments in which inherited alteration was claimed injpure material had been used. If io the experiments on beans quoted above, an ordinary impure commercial variety is used in place of a pore strain, selection of seeds of different sizes will lead to the isolation of individual strains, with different sizes of seed. But once these new pure strains are established, further selection will be of no avail. mm gfe U

(SPjciAW.l ▼Rrnsar *o» raf - PBISS; [By Db. 0. H. Feankix ]

field crops 01* in breeds <rf at first successful, but goon limits —in animals usually than in seli-fertilising to the continuous individuals. Another xeaifc quired characters appear to k?* mitted is to be found in tfe fluence of the mother OTgtj»J *; child, as the source ol during the early stages of This "induction" naturally |9HI in higher animals than in hnwsSfl and - plants, since in the period of pregnancy longer. Thjs factor, wtiefc-f* marked in man, has, howomJyP in common with fluence rarely lasts far or two generations. FuHtf&Jjii cases of a sudden chaoge,flf3B have been confounded wttbwfKi tancc of acquired I "mutations," about wMc& ntafiffi , said in a further article, an entirely different Mutations arise the regular consequence external conditions; an<} are generally not useful afaSH changes of external coaditiai?i ; Husbandry and SroAfcJ'v» If acquired characters axS! herited during the life living organism, a gloomy sUmI to fall on many of oar even on the future of «ar «Ip'm If these acquisitions are inanS how can the designed VOmM living matter be lasting. SnanS conducted alongside those viaafc||| the above resnlts have *mW\ breeding, though using individual and usually is, most sneeMf&'w' from the vast matei-in] jgmjU' nature or by artificial ewKllni lines are selected which pMM|s|Wfe inheritable characters. - 3§M W however, are found by genies, not the selected a&kb«k themselves. A large-sized l*p4 la a wheat crop may owe its chaz&fettfhff to favouring ciroumstanece «£ ,lj» £ superior inheritable disposition Qirif the test of its progeny, alongnfriMi ordinary stoek of the detect which of 'the two is the ffljPjp" principle of the differentiation peajance" and "inheritance,* iHb mental in all scientific effort to Ibm| living organisms, illustrates the fflf| ence between "husbandly" and TOf! ■ iag." The task of the first is to rii| ' individual perfection by 'jmmdag optima! c&ctanHtances; 'that tt the second, to effect permanent, lutngL | improvements to the inherited ufaM

"the race." ffifl Racial Myanca. J| I In the sphere of domestic plaid|»J animals, husbandry and well defined, although not ciently so in the minds of breeders. Much more clarity, is required, where man hirowlf ■ & cerned. Nobody will deny ftrf % species is capable of many ways; but it is essantialift fe ticguish here also between and "breeding." Husbandry—dividual Hygiene" as one may —comprises all our endeavotccs topj feet body and mind. Educafaco widest sense, hygienic living, a well-balanced food-ratio, treatment, exercise in the are doubtless of the highest tdgglli raising the standard of BMPW-jRi physical health. But it is fallacious, it is dangerous ta that they make the slightest bution towards o£ "the race." On the eoriaqjjH|| move conditions which faToat. velopment of tuberculosis, for a*MMB does not work for decreased resistance to "Individual hygiene" pntMH mination of the unfit by natural selection. All that races under highly civiferf «ll' ditions rapidly "breed the London Observer in an editorial note. hygiene" cannot stop it, hygiene" becomes a necessity. ' Fundamental It&wa of IfiWflPjji Sentiment and ignorance jWWjBP approach to this problem, the.JMR man was ever set to solve. wiil be overcome, as throughout development, once the neeewpHH conies imperative. But our JfflfJjMM of human heredity and of secondary factors involved | problem of eugenics is j scanty, although, of course, tj» Wjl fundamental laws of bere4itff®jj| doubtedly apply to man animals and plants. enormous increase in our fc-4WHS and without utilising even JW ■■l gained so far, any eugenM<l|*lH| ments are more than quote Baur, Fisher and *3ll (Human Heredity, London, "Legislative interference in iW'jjy.j|l population and racial default of such scientific no more than the salvery of uninsti'iictcd minatjon, ai' sterilisation, Qf-r-jjSll is possibly a wise step, but based on sound scientifia It is good news that a experts —biologists and besides medical often aro unfamiliar with mental facts —has been SMjHHI England to investigate may hope that this is the sWHHHI atari of "racial — 1 — ' ~ B