# 1922 Encyclopædia Britannica/Eugenics

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​EUGENICS (see 9.885*), the name coined by the late Sir Francis Gallon (from Gk., eiryecifa, well-born), and first used by him in his work on Human Faculty (1883), for what he defined as the "science of improving stock, which is by no means confined to questions of judicious mating, but which, especially in the case of man, takes cognizance of all influences that tend, in however remote a degree, to giving more suitable races or strains of blood a better chance of prevailing over the less suitable than they otherwise would have had." The word " science " used in this connexion is apt to be a little misleading. "Science" is used to denote two different things; it may mean the knowledge of a particular group of the laws of nature, or it may be used to denote the art of applying this knowledge in order to effect a desired object. It is clear from the context that it was in the second sense that Galton intended to use the word "science," and therefore a shorter and perhaps less ambiguous definition of eugenics would be "the application of our knowledge of the laws of heredity to improving the quality of the human race."
The aim of eugenics is therefore not primarily the collection of facts, but the construction and advocacy of practical proposals. The character of these proposals will of course depend on our conception of the laws of heredity, but the study of these laws forms the subject matter of the science of genetics. Genetics is a department of biology; and the last word in all controversies connected with heredity must rest with the biologist.
Like all the other laws of nature, the laws of heredity can only be ascertained by the carrying out of carefully thought-out experiments under standard- conditions. It thus follows that these laws must be investigated by dealing with animals and plants since we are not allowed to subject our fellow-beings to experiments or to control their mating. When we deal with human statistics we must therefore interpret them according to the laws which we have deduced, from our standardized experiments on the lower organisms, and in working with these statistics, the help and criticism of skilled mathematicians constitute invaluable aids to research, but mathematics applied to data unsifted by the biologist are valueless.
The popular conception of the best method to improve our race is to improve the environment, and for measures of this kind the American investigators have adopted the term euthenics.
"All men are born free and equal, " stands in the fore-front of the American constitution; and it is assumed that the differences between them are due to differences in up-bringing, to their mental and material circumstances in fact. If this supposition were justified it followed that the great remedy for many of our social ills was the extension of education, and on this supposition the social reformers of the 19th century have proceeded. Now it may be conceded that in order to bring out the full potentialities of any organism a favourable environment is necessary; if the soil be too dry the seed will either not germinate at all or if it does germinate it will produce but a poor and sickly plant; but all gardeners know that no amount of moisture or manure will ever produce from seed of inferior stock the plants which can be raised from fine varieties. If the poultry-keeper wishes for a large egg supply he must choose the breeds of fowl which he will keep; no matter how he feeds the inferior breeds he will not obtain from them a good yield of eggs.
One of the first questions therefore which presents itself to the eugenist for solution is whether the mental and moral qualities of men are inherited according to the same laws as govern the production of eggs by fowls. Gallon endeavoured to find an answer to this question, but the means which he adopted were decidedly crude. For instance, he obtained records of what he termed the good tempers and bad tempers of married people and tried to find out what proportion of the children were good-tempered or bad-tempered; and again he went through old lists of the results of examinations at Cambridge, and tried to show that a large proportion of the sons of those who had attained distinction in these examinations later rose to occupy important positions themselves. These methods certainly did give indications that character and ability were inherited, but they were open to grave objections. Thus it might be said that estimates of good temper and bad temper on the part of observers were un-analyzed haphazard impressions incapable of accurate measurement; and again, so far as the inheritance of mental ability was concerned, it was pointed out that a boy could inherit from his mother as strongly as from his father, and that in the case of Cambridge scholars there were no means of ascertaining the mental capacities of the mothers.
Since Galton's time, however, enormous strides have been made in attacking the problem of accurately measuring mental ability. The extension of compulsory education to all the children of the leading nations of Europe and the standardization of the curricula of education have provided investigators of mental ability with a very large amount of material. After many years' work and thousands of trials on the children of the elementary schools of Paris, Drs. Simon and Binet succeeded in elaborating a series of tests by means of which they could measure the degree of intelligence attained by growing children. The distinctive feature of these tests was their independence of any special type of instruction. They were so framed that, for example, a child on attaining the age of three could be reasonably expected to do the things prescribed for a child of three, and fail to do those allotted to a child of four. For instance:—
At 1 year a child should recognize food.
At 2 years (1) walk; (2) obey a simple direction.
At 3 years (1) point out nose, eye and mouth; (2) repeat two digits; (3) enumerate the objects in an engraving; (4) tell his surname ; (5) repeat a sentence with six syllables.
At 4 years (1) tell whether it is a boy or a girl; (2) name a key, knife and a penny; (3) repeat three numerals; (4) point out the longer of two lines.
At 5 years (1) discriminate the heavier of two boxes; (2) copy a square; (3) repeat a phrase with 10 syllables; (4) count four pennies; (5) reconstruct a card cut diagonally into two pieces.
Similar tests were devised suitable lo the inlelligence of children of every age up to fifteen. At this age the growth of mental capacity as distinct from attainment seems to be complete. If a child of three could perform the tests arranged for a child of four he was said to be advanced; if he could only perform those suitable for a child of two he was said to be backward. ​This scale devised for the school children of France has been tested in the elementary schools of Italy and of the United States. It has been found to be right in principle, although tests and ages require some slight adjustment when applied to children of other races than the French.
Now when we apply these tests to the unfortunate people denominated imbeciles and feeble-minded, we make the surprising discovery that some of them, although they may live to an advanced age, are never able to perform the tasks allotted to a child of three and that none of them can do more than pass the tests suitable to a child of ten. Here then is the explanation of mental defect; it is the failure of the mind to develop further than to a certain stage. The next step was to ascertain whether or not this unfortunate character was hereditary, and the merit of solving this, perhaps the most important of eugenic problems, must be accorded to Dr. Goddard, a doctor attached to the staff of the Vineland Institution for insane and mentally defective children in the state of New Jersey. This institution is a charitable one, which takes in defective children and gives them the best education which they are capable of receiving. All the inmates are tested on admission, and at suitable intervals afterwards, by the Simon-Binet scales.
Now Dr. Goddard secured the services of a certain number of educated investigators, who received a special course of training in the institution itself and were then sent forth to investigate the ancestry of the inmates so far as this could be accomplished. This they did by gaining the confidence of the relatives of the inmates, to whom the acceptance of the care of their afflicted children by the Vineland Institution was a great boon, and who were naturally anxious to learn about their progress and quite ready to talk about the first appearance of what to them was an ordinary malady. In this way the investigator was enabled to find out whether any of the brothers or sisters of a particular child were mentally defective, whether his parents or his grand-parents had been similarly affected, or whether there were circumstances pointing to some accident as the cause of the trouble. By proceeding along these lines it was possible to draw up an ancestral chart for each inmate of the institution. In this chart a square indicated a male relative, a circle a female; if it appeared that the relative was mentally defective the square or circle was blackened—if on the other hand the relative was clearly normal a square (or circle as the case might be) with the letter N inscribed was placed on the chart. Where definite information was lacking a blank square or circle was added.
The chart was revised at intervals, a fresh investigator being employed for the research on which the revision was based. In practically no case did renewed inquiry lead to the conclusion that relatives formerly regarded as defective were really normal; on the contrary, at every fresh examination more doubtful cases resolved themselves into definitely feeble-minded ones and the child's chart was correspondingly blackened.
The net results of Dr. Goddard's investigations were as follows. In the case of 6,000 children a mentally defective ancestor was ascertained; and about one-fourth of these children were definitely feeble-minded and about one-fourth definitely normal; the mental condition of the remainder could not be ascertained. In the case of 1,500 children there was a definite history of an accident which might be regarded as the cause of the mental condition, and 804 children are classified as of "neuropathic" ancestry, i.e. the descendants of epileptic or hysterical parents, a condition which seems akin to feeble-mindedness. It should be remarked that these numbers included not only the inmates of the institution but their brothers and sisters and cousins who were outside and many of whom were quite normal mentally. Where both parents were mentally defective practically all the children were feeble-minded: out of 750 such children investigated only six were reported as normal; and considering the low grade of sexual morality maintained by such people the parentage of these children must be the subject of considerable doubt. In the case of one such family, where both parents were mentally defective, two children out of a large number were normal but these two were black and therefore of obvious illegitimate origin. Where one parent was defective and the other, though normal, had a defective ancestor, then as a rule some of the children in the family were defective and others normal. The same results were obtained where both parents themselves were normal but where one of them was descended from a defective ancestor.
Now these results are in accord with the newest and best-attested results of researches into the inheritance of certain characters in the lower animals and in plants; the laws governing this kind of inheritance are termed Mendelian because they were first ascertained by Gregor Mendel, an Augustinian monk in the middle of the igth century. Mendel's work was unnoticed by most of his contemporaries and was only rediscovered and confirmed by further research in 1900. Briefly the laws which he discovered may be summarized thus:—
(1) In different breeds or strains of the same species characters often appear in pairs so that only one of the pair appears in one strain: such characters are termed allelomorphs. (2) When two such strains are crossed, in the first generation of hybrids only one of the allelomorphs appears: this is termed the dominant character; the allelomorph which fails to appear is termed the recessive character. (3) If the first generation of hybrids be used as parents of a second generation of hybrids, one-fourth of these will exhibit the recessive character, and these if used to propagate a further generation will give rise to nothing but recessives for however many generations propagation may be carried on. (4) In cases (such as plants) where self-fertilization is possible the three-fourths of the second hybrid generation which exhibit the dominant character can be individually tested as to their hereditary potentialities. It is then found that one-third of them (i.e. one-fourth of the whole generation) give rise to nothing but dominants, but the remainder (i.e. one-half of the whole generation) behave as did the first generation of hybrids, i.e. each gives rise to progeny three-fourths of which exhibit the dominant character and one-fourth the recessive character.
These results were interpreted by Mendel as proving that the first generation of hybrids produced two kinds of germ cells in equal numbers, each kind bearing one of the allelomorphic characters, and that these two kinds were mixed at random in fertilization. Bateson and Punnett later gave reasons for believing that the recessive quality of a character was due to the fact that it was caused by the absence of something which was present in the dominant, and that when two germ cells united in fertilization, if one of them bore the dominant character, that was sufficient to ensure the appearance of that character in the resulting organism.
Menfal defect is therefore a recessive character due to the want of something in the fertilized egg which gives rise to the mentally defective child, something which is present in the germ from which the healthy child originates. We now understand why two defective parents can give rise only to defective children and why a normal child can spring from the union of a normal and a defective parent, and further why such a child may in turn give rise to defective children as well as to normal ones.
The social implications of this discovery are fundamental and far-reaching. We see at once and this is in accordance with the experience of the Vineland authorities why all efforts to raise the mentally defective above a certain level by education are bound to fail. Further, we see that unless such defectives are segregated for life and prevented from breeding they constitute a constant source of potential poison to the race.
If we regard all children who fail to attain a greater mental age than nine as defective, they can be conveniently arranged in three groups, viz. (a) those who never attain a mental age of more than three years, who are termed idiots; (b) those who never attain a mental age of more than six years, who are termed imbeciles; whilst (c) those reaching mental ages of seven, eight and nine years are termed in English law "feeble-minded," but by the American authorities "morons" (Gk., μώρος, foolish). Neither idiots nor imbeciles constitute a social danger since their incapacity is so great that they are unable to support themselves in the ordinary battle of life and must therefore be maintained ​ in institutions, but morons possess sufficient intelligence to struggle along in the lowest social grade and in the poorest-paid employments, and it.is just these grades of society which produce an enormous crowd of children which in former times died out but which our philanthropists now endeavour to keep alive at the expense of taxes levied on the better grades of society.
The gradual lowering of the grade of mental capacity in the whole population which must result from these conditions is not the full extent of the evil. Not only are the morons defective in intelligence, they are also defective in self-control which is the basis of all morality. American investigators have applied the Simon-Binet tests in certain large American cities to the delinquents who appear before police-courts: and their results point to the conclusion that a large proportion of the thieves, prostitutes and habitual drunkards are mental defectives. In one case, to give one example, it was found that 50% of prostitutes were indubitably feeble-minded and this proportion was arrived at when a large number of doubtful cases had been put down as normal. There seems to be no tendency such as Lombroso postulated in these unfortunates to commit crime for its own sake; their crimes are simply due to an inability to control the tendency to the gratification of their own desires and passions, irrespective of the consequences to others and to themselves.
Dr. Goddard points out that there are two totally different kinds of inebriates to be met with, viz. (i) ordinary people who have lapsed into drinking habits but who are quite capable, if they become sufficiently frightened, of being completely cured, and (2) morons, ready to repent with tears and to sign any pledge, but certain within a week to plunge again into intemperance.
These conclusions which run counter to so many popular prejudices have naturally awakened much criticism and opposition. It should be stated that Dr. Goddard's work has been repeated at various places in the United States, and that similar results have been obtained, but it is to be feared that in many cases his extreme care and the constant repetition of his investigations which he practised have been omitted. Hence Dr. Heron and Prof. Pearson have pointed out that the methods of ascertaining the degree of mental defect were often extremely unsatisfactory and unconvincing and Goddard's methods of ascertaining the feeble-mindedness of the parents and other relatives of feeble-minded children have been criticized as being based on impressions which the investigators derived from mere gossip. On the face of it there is much in this objection, but on the whole Goddard's answer to it is satisfactory. He says first that the investigators were carefully trained so that their judgment could be relied on, and secondly that when different investigators examined the same case, at considerable intervals, they arrived at concordant results. From the point of view of students of heredity it is of far greater importance that the inheritability of mental defect should have been established in the carefully standardized investigations of Dr. Goddard than that obvious blunders should have been demonstrated in many of the parallel investigations carried out elsewhere.
A school of English social reformers of which Dr. Saleeby has been a prominent member have endeavoured to account for most of these cases of mental defect by the action of what they term racial poisons. They maintain that alcohol, when drunk in immoderate amounts, and the toxins of the venereal disease syphilis both attack the germ cells carried in the parents' bodies and not only tend to cause the production of diseased and defective children but that these children if they survive and reproduce likewise give rise to imperfect offspring. Now it is conceded on all hands that the toxins of syphilis do in certain cases penetrate the placenta, and interfere with the growth of the embryo; nay more, that the embryo itself may become infected. As a result horribly malformed and diseased infants are born, but when these survive they appear to get rid of the syphilitic infection before the completion of adolescence, and there is no reliable evidence that their germ cells are defective or diseased.
With regard to alcohol it seems clear that immoderate in- dulgence in alcohol about the time of conception and during pregnancy tends to produce children with weakened constitutions, but again there is little or no evidence that their germ cells are weakened. It is true that one investigator (Stockard) claims to have proved that by making guinea-pigs inhale the vapour of absolute alcohol for several hours daily he succeeded in causing them to produce weakened offspring. In these young guinea-pigs injuries to the eyes and nervous system were prominent, and these weaknesses were transmitted in increased degree to subsequent generations without further exposure to the influence of alcohol. The stock died out in the fourth or fifth generation. It would, however, be exceedingly rash to generalize from these experiments. Pearl repeated them, using the domestic fowl instead of the guinea-pig, and found that the chicks produced by alcoholized parents were on the whole hardier than those whose parents were left untouched. The present writer has repeatedly introduced large quantities of absolute alcohol by subcutaneous injection into the bodies of white mice, so that they passed into a state of complete insensibility, yet even after repeated treatment of this kind they recovered and became the parents of offspring which were apparently quite healthy. Finally, considering the enormous extent to which alcohol has been consumed by the British nation during the last 300 years it is obvious that if any permanent injury had been done to the germ cells, it should be now a diseased and crippled nation instead of a virile people such as it sufficiently proved itself to be in the World War of 1914-8. That the causes of mental defect cannot be found in the alcoholism of the parents was definitely proved by Goddard. Of 300 children born of defective parents not alcoholic 99% were mentally defective; and of 130 children born of alcoholic defectives 985% were defective.
Mental defect must be assigned to the same cause as that which produces other types of Mendelian recessive. It is the common experience of all who have bred large numbers of animals or cultivated large numbers of plants, that from time to time Mendelian recessives turn up, and no more definite cause for their appearance has ever been suggested than that of "accidents of division" in the ripening germ cells. These recessives in many cases show varying degrees of defect which closely recall the grades of mental defect met with amongst the feeble-minded. For instance, in the cultures of the fruit-fly Drosophila ampelophila made by Prof. Morgan and his pupils various grades of blindness have appeared. The normal pigment necessary to the function of vision is of a dark red colour: complete albinos in which the eyes are white frequently occur, and also various imperfect grades of red classified by Morgan as cherry, eosin, etc. The occurrence of these defectives in the fruit-fly is certainly not attributable either to syphilis or to alcohol, and there is no more reason to attribute the occurrence of mental defectives in the human race to these causes than there is to assign these "race-poisons" as causes of the defectives in the fruit-fly.
As the results of the inquiry into the nature of human heredity are so startling and seem to involve such grave consequences it is obviously the first step in eugenic endeavour to make them as widely known as possible, so as to prepare public opinion for the practical steps which sooner or later must be taken. With this object the Eugenics Record Office was established in America by the Carnegie trustees and placed under the able presidency of Dr. Davenport. In England Sir Francis Gallon by a bequest in his will founded a chair of Eugenic Research in University ​College, London, to which his friend Prof. Karl Pearson was appointed. Prof. Pearson has established a biometrical laboratory in which a large amount of valuable statistical work has been accomplished and much evidence adduced bearing on such questions as the inheritability of consumption, etc. The Eugenics Education Society, the object of which was not research but an endeavour to make the results of research widely known, was founded in London under the honorary presidency of Sir Francis Gallon. Its first president was Sir James Crichton-Browne, its second president Mr. Montagu Crackanthorpe, to whom succeeded Maj. Leonard Darwin in 1911.
The cause of eugenics owes a great debt to Maj. Darwin for having pointed out clearly wherein fitness to survive in the eugenic sense really consists. On this subject much confusion has reigned not only in the minds of the general public but also in the minds of the first enthusiasts for eugenic reform. Attention was at first concentrated on physical health and muscular development, and it was an easy task for opponents to point out that the "big blonde beast" of Nietzsche was not the most desirable type of man, and that men of great talent and initiative often were so in spite of the handicaps of physical disease or infirmity, that Caesar and Mahomet both suffered from epilepsy and that Robert Louis Stevenson died of consumption.
As Bateson has well put it: "We animals live not only on account of but in spite of what we are." Maj. Darwin has emphasized the fact that the decisive factor in the human struggle for existence is general ability and that, broadly speaking, when we compare together members of the same profession the greater the ability the greater the pay.
It is an easy task for the critic to point to individuals who though able and virtuous have become poor, and to others who though rich are idle and vicious, but these exceptional cases do not detract from the generalization insisted on by Maj. Leonard Darwin that on the whole the poor deserve to be poor and that their ranks are continually swollen by the descent of the unfit from the superior strata of society. It may be added that if the rich persist in being idle and vicious then riches have a strong tendency to disappear a fact borne witness to by the Lancashire proverb, "It takes three generations to pass from clogs to clogs"; further, that if the able and. virtuous poor persist in well-doing they invariably rise to affluence in one or two generations, so that these apparent exceptions to Maj. Darwin's generalization have a way of righting themselves.
Birth Control
The Dean of St. Paul's (the Rev. Dr. Inge), a prominent member of the Eugenics Education Society, has pointed out that during the first half of the 19th century, when no free education was provided, there were far more emergences of men of talent and ability from the masses than during the second half when every effort had been made to "raise the poor" by education, sanitation and doles. Maj. Darwin has called attention to the discovery of harmless and painless means of sterilization by X-rays: so that limitation of the birth-rate by preventing conception is now easily accomplished.
Formerly the natural fecundity of all classes of society was allowed to flow on unchecked: even under these circumstances larger families were born to the poor than to the rich because the poor marry early and improvidently, which is one of the main causes of their poverty, but the greater death-rate amongst their children prevented the poorer strata of society from increasing relatively to the rich. Now, however, the rich limit their families to a number which they can easily support, and this number tends to become smaller and smaller as heavier taxation is levied to provide for the survival and education of large families of the poor. Eugenists contend that the State is in this way deliberately cutting off its best stocks which raised it to greatness in the past, and on the continuance of which its whole future depends. Against this whole policy the Eugenics Education Society has raised a continuous protest and the Eugenics Record Office of America has published a valuable series of bulletins showing the awful progeny of criminals, paupers and lunatics that have sprung from a single worthless family during the last 100 years, and some American states have passed somewhat hastily conceived laws designed to cause criminals and idiots confined in state prisons to be sterilized.
It is indeed obvious that mere restraint of marriage will avail little since it by no means prevents illegitimate union, and amongst the lowest strata of society the marriage ceremony is frequently dispensed with. The only way in which the cruel methods of natural selection can ultimately be avoided is by the sterilization of the unfit; in a word, by preventing parents who are unable properly to support the offspring which they have already produced from producing any more. A first feeble step in this direction may be found in the regulation which until recently was enforced in English poorhouses, forbidding husbands and wives to live together, but public opinion would now be opposed to any extension of this principle: people generally are so obsessed with the liberty of the subject that the liberty of the depraved and worthless to pollute society by a stream of worthless progeny has not been seriously challenged.
The reckless reproduction of the poor in England is sometimes defended on the ground that it contributes to the population of the British overseas dominions and so to the up-building of the British Empire. But on closer analysis we find that this defence will not hold. The great British dominions have very clear conceptions about the type of immigrant whom they desire and whom alone they will admit. They desire people of initiative and adaptability and these are just the qualities which are lacking in our submerged tenth. Incidentally the submerged tenth are without the means of emigration, and the dominions have wisely refused to accept immigrants who come to them on "assisted passages." As things were in 1921 England was being threatened more and more with the fate of becoming a reservoir of the unfit, since it is the fit who both emigrate and limit their families in accordance with their means. The Dean of St. Paul's has pointed out that between the years 1700 and 1800 the population of Great Britain increased by 30% but that between 1800 and 1900 it increased by no less than 300%. Statistically, therefore, it appears that the' British Isles are rapidly approaching a condition of over-population, even if they have not already attained it. What is needed is not an increase in the birth-rate but a rigorous selection of those who are to be the parents of the future generation. In former ages this selection was accomplished by famine and pestilence. Ireland in 1846 had eight millions of starving peasantry living a life little better than that of the pigs which they housed in their cabins. The famine and emigration in 40 years reduced the population to four millions who might be described as thriving farmers. The Black Death in the 14th century wiped out two-thirds of the population of England: the following century was the most prosperous and happy time for the agricultural labourers of England of which there is any record. Well has it been said: "In the good old days people died in the country as fast as they now die in the slums of cities, and they died in the cities as fast as white people die on the coast of Guinea." If things go on as they are such a selection will again sooner or later be accomplished by nature; the whole purpose of eugenic propaganda is to make clear that we are approaching such a catastrophe; and to endeavour by humane and wise methods to avert it; to so arrange matters by legislation that the enterprising and provident shall be the parents of the future race and that drunkards, wastrels and reckless shall be debarred from handing on their vices to posterity.
See Francis Galton, Hereditary Genius (1869; 2nd ed. 1882); Human Faculty (1883); Essays in Eugencis (Eugenics Education
Society, 1909); Edward Schuster, Eugenics (1913); W. C. D. Whetham and C. D. Whetham, Introduction to Eugenics (1912), Heredity and Society (1912), The Family and the Nation (1909); C. B. Davenport, Heredity in Relation to Eugenics (1911); H. H. Goddard, Feeble-mindedness: its Causes and Consequences (1914); The Kallikak Family: a Study in the Heredity of Feeble-mindedness (1912); A. F. Tredgold, Mental Deficiency (Amentia) (2nd ed. 1914); Alfred Binet and Th. Simon, translated by Clara Town Harrison, A Method of Measuring the Development of the Intelligence of Young Children (1912); Paul Popenoe and Roswell Hill Johnson, Applied Eugenics (1920).
(E. W. MacB.)
* ↑ Natural Inheritance (1889).
* ↑ Hereditary Genius (1st ed. 1869, 2nd ed. 1892).
* ↑ For a full account of these tests see " The Measurement of Intelligence," by Dr. T. Simon (trans, by Dr. W. C. Sullivan), The Eugenics Review, vol. vi., No. 4, Jan. 1915.
* ↑ 1 H. H. Goddard, Feeble-mindedness (1914).
* ↑ W. Bateson and R. C. Punnett, "A Suggestion as to the Nature of Walnut Comb in Fowls," Proc. Camb. Phil. Soc., vol. xiii , 165. See Mendel's Principles of Heredity, by W. Bateson (1919).
* ↑ Report of the Massachusetts Commission for the Investigation of the White Slave Traffic so-called.
* ↑ David Heron, Mendelism and the Problem of Mental Defect: I. A Criticism of Recent American Work, Biometric Laboratory Publications (Questions of the Day), No. 7.
* ↑ Karl Pearson and Gustav Jaederholm, Mendelism and the Problem of Mental Defect: II. The Continuity of Mental Defect, ibid., No. 8. Mendelism and the Problem of Mental Defect: HI. The Graduated Character of Mental Defect, etc., ibid., No. 9.
* ↑ C. R. Stockard and Dorothy Craig, "An Experimental Study of the Influence of Alcohol on the Germ-Cells," Archiv für Entwicklungsmechanik, vol. xxxv. (1913).
* ↑ C. R. Stockard and George N. Papamcolaou, "Further Studies of the Modification of Germ-Cells," Jour. Exp. Zool., vol. xxvi. (1918).
* ↑ R. Pearl, " The Experimental Modification of Germ-cells," pt. .i., Jour. Exp. Zool., vol. xxii. (1917).
* ↑ Materials for the Study of Variation (1894).
* ↑ "Presidential Address to the Eugenics Education Society," Eugenics Review, Oct. 1914.
* ↑ Outspoken Essays (1920).
* ↑ A. H. Estabrook and C. B. Davenport, The Nam Family, Eugenics Record Office (1912).
* ↑ Indiana, Washington, California, Connecticut, Nevada, Iowa, New Jersey, New York, North Dakota, Michigan, Kansas, Wisconsin. For details see Popenoe, Applied Eugenics, pp. 1914.