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A . Pigment of Cho¬ roid Coat and Pigment of Iris Absent. 1. The Albino eye. Red from unobscured blood vessels.

I>. Pigment of Cho¬ roid Present.

a. Iris without True Pigment. 2. Blue. Due to a purple layer on back of eye.

p. Iris with True Pigments.

a. Lipochroiue or yellow ■pigment. 3. Green or cat eye. Yellow pigment on blue background.

b. M elanic or black pig¬ ment. 4. Hazel pr gray eye. Dilute brown pig¬ ment around pupil only.

5. Brown eye. Melanie pigment ; various shades from various dilutions.

6. Black eye. An abundance of melanic pig¬ ment. \

EYE COLORS IX MAN

HEREDITY IN RELATION TO EUGENICS

BY

CHARLES BENEDICT DAVENPORT *

CARNEGIE INSTITUTION OF WASHINGTON DIRECTOR, DEPARTMENT OF EXPERIMENTAL EVOLUTION COLD SPRING HARBOR, LONG ISLAND, N. Y. SECRETARY OF THE EUGENICS SECTION AMERICAN BREEDERS’ ASSOCIATION

NEW YORK

HENRY HOLT AND COMPANY 1911

5\5Z

COPYRIGHT, 1911 BY

HENRY HOLT AND COMPANY

5*7 5~

3) Z1 V

PRESS OF T. MOREY 4 SON GREENFIELD, MASS., U. S. A.

TO

MRS. E. H. HARRIMAN

IN RECOGNITION OF THE GENEROUS ASSISTANCE SHE HAS GIVEN TO RESEARCH IN EUGENICS THIS BOOK IS GRATEFULLY DEDICATED

PREFACE

Recent great advances in our knowledge of heredity have revolutionized the methods of agriculturalists in im¬ proving domesticated plants and animals. It was early recognized that this new knowledge would have a far- reaching influence upon certain problems of human society the problems of the unsocial classes, of immigration, of population, of effectiveness, of health and vigor. Now, great as are the potentialities of the new science of heredity in its application to man it must be confessed that they are not yet realized. A vast amount of investigation into the laws of the inheritance of human traits will be required before it will be possible to give definite instruction as to fit marriage matings. Our social problems still remain prob¬ lems. For a long time yet our watchword must be investi¬ gation. The advance that has been made so far is chiefly in getting a better method of study.

In this book I have sought to explain this new method. An application of this method to some specific problems, especially to. the transmission of various human traits and susceptibilities to disease, has been attempted. The sug¬ gestions made are by no means final but are made to illus¬ trate the general method and give the most probable con¬ clusions. Only with much more accurate data can the laws of inheritance of family peculiarities be definitely de¬ termined.

Some general consequences of the new point of view for the American population have been set forth in Chap¬ ters IV to VI. Their essential truth will, I trust, be generally

in

IV

PREFACE

recognized. In any case it will not be amiss to point out the fundamental difference between the modern eugenical and the contrasted or "euthenical” standpoints. As a matter of fact the eugenic teachings that we think of as new are very old. Modern medicine is responsible for the loss of appreciation of the power of heredity. It has had its atten¬ tion too exclusively focussed on germs and conditions of life. It has neglected the personal element that helps determine the course of every disease. It has begotten a wholly impersonal hygiene whose teachings are false in so far as they are laid down as universally applicable. It has forgotten the fundamental fact that all men are created bound by their protoplasmic makeup and unequal in their powers and responsibilities.

As indicated, it is the aim of this book to incite to further investigation. Some space is devoted to the eugenics move¬ ment a movement which it is hoped will, in this country, for the present, take mainly the form of investigation. To this movement the Eugenics Record Office (a branch of the work of the American Breeders’ Association) is dedicated. The Eugenics Record Office wishes to get in touch with all persons interested in the eugenics movement. It invites every person who is willing to do so to record his heritage and place the record on file at the Record Office. "Drop a postal card” at once to the Eugenics Record Office, Cold Spring Harbor, New York, and ask for the blank schedule they furnish. It is understood that all data deposited in this way will be held as confidential and be used only for scientific purposes. The data received are carefully pre¬ served in a fireproof vault and indexed so as to be avail¬ able to the student. Specifically, the Record Office seeks pedigrees of families in which one or more of the following ' traits appear: short stature, tallness, corpulency, special talents in music, art, literature, mechanics, invention and ;

PREFACE

v

mathematics, rheumatism, multiple sclerosis, hereditary ataxy, Meniere’s disease, chorea of all forms, eye defects of all forms, otosclerosis, peculiarities of hair, skin and nails (especially red hair), albinism, harelip and cleft palate, peculiarities of the teeth, cancer, Thomsen’s disease, hemo¬ philia, exophthalmic goiter, diabetes, alkaptonuria, gout, peculiarities of the hands and feet and of other parts of the skeleton. We do not appeal primarily to physicians for this information but to the thousands of intelligent Americans who love the truth and want to see its interests advanced. At the same time, physicians can aid in the work by in¬ ducing persons with bodily or mental peculiarities that run through their families to send to the Record Office for blank schedules on which to record the method of inherit¬ ance of the trait in question. Thus every one can share in the eugenics movement.

The Eugenics Record Office will be glad to assist in the establishment of local eugenics societies which shall become centers for the study of local blood-lines and for local in¬ struction. The Office seeks to assist state officials in the study of the classes which are supported and protected by the State, and to assist the States to locate the centers in which their defectives and delinquents are being bred. It is believed that a little money spent in studying the sources of reproduction of persons who are destined to become state wards will prove a highly profitable investment, since it may lead to steps that will diminish such reproduction.

In the preparation of the present volume the author has been aided by many hands. Professor James A. Field, of the University of Chicago, has kindly read the proof and made valuable suggestions. The bibliography and the pedi¬ gree charts were largely prepared by Miss Amey B. Eaton, of the Eugenics Record Office. Professor E. B. Wilson has generously granted me the use of Figures 1 to 6 from his

VI

PREFACE

invaluable book, “The Cell in Development and Inherit¬ ance.” Hundreds of persons have voluntarily contributed the data upon which the conclusions that have been drawn are based. My friend and colleague, Mr. H. H. Laughlin, Superintendent of the Eugenics Record Office, has assisted in many points and has contributed the frontispiece. My wife has, as usual, revised the manuscript and prepared it for the printer. The Trustees of the Carnegie Institution have granted me exceptional opportunities for the prosecu¬ tion of the work. Last, but by no means least, this work and the collection of data out of which it has grown have been made possible by the financial assistance and by the personal stimulus and advice given by the lady to whom, in insufficient recognition, this book is, with her permis¬ sion, dedicated. To all those who have so kindly assisted me I return thanks. I trust the book will be useful to hu¬ manity, so as to justify them for the pains they have taken to bring it to pass.

C. B. D.

Carnegie Institution of Washington Station for Experimental Evolution Cold Spring Harbor, N. Y.

CONTENTS

CHAPTER I

EUGENICS: ITS NATURE, IMPORTANCE AND AIMS

PAGE

1. What Eugenics is . 1

2. The Need of Eugenics . 2

3. The General Procedure in Applied Eugenics . 4

CHAPTER II

THE METHOD OF EUGENICS

1. Unit Characters and Their Combinations . 6

2. The Mechanism of the Inheritance of Characteristics . . 10

3. The Laws of Heredity . 16

4. Inheritance of Multiple Characters . 20

5. Heredity of Sex and of “Sex-limited” Characters .... 21

6. The Application of the Laws of Heredity to Eugenics . . 23

CHAPTER III

THE INHERITANCE OF FAMILY TRAITS

1. Eye Color . 27

2. Hair Color . 32

3. Hair Form . 34

4. Skin Color . 36

5. Stature . 38

6. Total Body Weight . 43

7. Musical Ability . 48

8. Ability in Artistic Composition . 51

9. Ability in Literary Composition . 54

10. Mechanical Skill . 55

11. Calculating Ability . 59

12. Memory . 59

13. Combined Talents and Summary of Special Abilities ... 60

. . 61

-hiDWRITING . - . 63

Vll

Vlll

CONTENTS

PAGE

16. General Bodily Energy

17. General Bodily Strength

18. General Mental Ability

19. Epilepsy . . '2

20. Insanity . 77

21. Pauperism . 80

22. Narcotism . 82

23. Criminality . 83

24. Other Nervous Diseases . 92

a. The General Problem . 92

b. The Neuropathic Makeup .

c. Cerebral Hemorrhage .

d. Cerebral Palsy of Infancy .

e. Multiple or Disseminated Sclerosis .

/. Hereditary Ataxy .

g. Meniere’s Disease .

h. Chorea .

i. Huntington’s Chorea .

j. Hysteria .

25. \ Rheumatism .

26. Speech-Defects .

27. 'Defects of the Eye .

a. Anomalies of Iris .

b. Reduction in Size of the Eyeball .

c. Atrophy of the Optic Nerve .

d. Cataract .

e. Displaced Lens .

/. Degeneracy of the Cornea .

g. Glaucoma .

h. Megalophthalmus .

i. Nystagmus .

k. Paralysis or Imperfect Development of the Muscles of Eye

and Lids .

l. Pigmentary Degeneration of the Retina .

m. Night blindness .

n. Color blindness .

o. Myopia .

p. Astigmatism .

28. Ear Defects .

a. Deaf Mutism .

b. Otosclerosis .

c. Catarrhal Affections .

29. Skin Diseases . . .

a. Congenital Traumatic Pemphigus .

93

97

97

99

99

101

101

102

103

104

105

107

108

109

110 111 112 112 113 115 115

115

116 118 120 121 123

123

124

129

130

131

132

b. Psoriasis

c. Ichthyosis

CONTENTS

IX

PAGE

d. Thickening of the Outer Layer of the Skin . 135

30. Epidermal Organs . 135

a. The Skin Glands . 136

b- Hair . 138

c. Nails . I39

d. Teeth . 139

e. Harelip and Cleft Palate . 144

31. Cancer and Tumors . 146

32. Diseases of the Muscular System . 149

a. Thomsen’s Disease . 149

b. Certain Muscular Atrophies . 149

c. Trembling . 151

d. Hernia . 151

33. Diseases of the Blood . 152

a. Chlorosis . 152

b. Progressive Pernicious Anemia . 153

c. Nosebleed . 153

d. Telangiectasis . 153

e. Hemophilia . 153

/. Splenic Anemia with Enlargement of the Spleen . 157

34. Diseases of the Thyroid Gland . 158

а. Cretinism . 158

б. Goitre . 158

c. Exophthalmic Goitre . 159

35. Diseases of the Vascular System . 159

a. Heart . 160

b. Arteriosclerosis . 162

36. Diseases of the Respiratory System . 163

37. Diseases of the Alimentary System . 166

a. Diabetes Insipidis . 167

38. Diseases of Excretion . 168

a. Alkaptonuria . 168

b. Cystinuria and Cystin Infiltration . 169

e. Hematuria . 169

d. Urinary Calculi . 169

e. Gout . 169

39. Reproductive Organs . 170

a. Cryptorchism . 170

b. Hypospadias . 170

c. Prolapsus of the Uterus and Sterility . 171

40. Skeleton and Appendages . 171

a. Achondroplasy . 172

b. Scoliosis . 172

c. Exostoses . 173

d. Absence of clavicles . 173

e. Congenital Dislocation of the Thigh Bone Pelvis Joint . . 174

X

CONTENTS

PAGE

/. Polydactylism . 175

g. Syndactylism . 176

h. Brachydactylism . . . . . 177

i. Other Deformities of the Hands . 177

41. Twins . 180

CHAPTER IV

THE GEOGRAPHIC DISTRIBUTION OF INHERITABLE TRAITS

1. The Dispersion of Traits . 181

2. Consanguinity in Marriage . 184

3. Barriers to Marriage Selection . 189

A. physiographic barriers . 189

a. Barrier of Water . 190

b. Barrier of Topography . 196

B. SOCIAL BARRIERS . 198

c. The Barrier of the Social Status . 199

d. The Barrier of Language . 200

e. The Barrier of Race . 202

/. The Barrier of Religious Sect . 202

CHAPTER V

MIGRATIONS AND THEIR EUGENIC SIGNIFICANCE

1. Primitive Migrations . 204

2. Early Immigration to America . 205

3. Recent Immigration to America . 212

a. Irish . 213

b. Germans . 214

c. Scandinavians . 214

d. Austro-Hungarians . 215

e. Hebrews . 215

/. Italians . 216

g. Poles . 218

h. Portuguese . 218

4. Control of Immigration . 220

CHAPTER VI

THE INFLUENCE OF THE INDIVIDUAL ON THE RACE

1. Elizabeth Tuttle . 225

2. The First Families of -Virginia . 228

CONTENTS

xi

PAGE

3. The Kentucky Aristocracy . 230

4. The Jukes . 233

5. The Ishmaelites . 234

6. The Banker Family . 237

CHAPTER VII

THE STUDY OF AMERICAN FAMILIES

1. The Stuhy of Genealogy . 239

2. Family Traits . 241

3. The Integrity of Family Traits . 249

CHAPTER VIII

EUGENICS AND EUTHENICS

1. Heredity and Environment . 252

2. Eugenics and Uplift . 254

3. The Elimination of Undesirable Traits . 255

4. The Salvation of the Race Through Heredity . 260

5. The Sociological Aspect of Eugenics . 261

6. Freedom of the Will and Responsibility . 264

CHAPTER IX

THE ORGANIZATION OF APPLIED EUGENICS

1. State Eugenic Surveys . 267

2. A Clearing House for Heredity Data . 26°

Bibliography . 273

Appendix: List of Places Referred to, Geographically Arranged 289

Index . 291

PLATES

I. Eye Colors in Man . Frontispiece

II. Wave of Immigration into the United States, from all

Countries, 1820-1910 218

HEREDITY IN RELATION TO EUGENICS

5 I S'X S'! S'

CHAPTER I

EUGENICS: ITS NATURE, IMPORTANCE AND

AIMS

1. What Eugenics Is

Eugenics is the science of the improvement of the human race by better breeding or, as the late Sir Francis Galton expressed it: “The science which deals with all influences that improve the inborn qualities of a race.” The eugenical standpoint is that of the agriculturalist who, while recog¬ nizing the value of culture, believes that permanent advance t is to be made only by securing the best “blood.” Man is an organism an animal ; and the laws of improvement of corn and of race horses hold true for him also. Unless people accept this simple truth and let it influence marriage selection human progress will cease.

Eugenics has reference to offspring. The success of a marriage from the standpoint of eugenics is measured by the number of disease-resistant, cultivable offspring that come from it. Happiness or unhappiness of the parents, the principal theme of many novels and the proceedings of divorce courts, has little eugenic significance; for eugenics has to do with traits that are in the blood, the protoplasm. The superstition of prenatal influence and the real effects

1

2 HEREDITY IN RELATION TO EUGENICS

of venereal disease, dire as they are, lie outside the pale of eugenics in its strictest sense. But no lover of his race can view with complaisance the ravages of these diseases nor fail to raise his voice in warning against them. The parasite that induces syphilis is not only hard to kill but it frequently works extensive damage to heart, arteries and brain, and may be conveyed from the infected parent to the unborn child. Gonorrhea, like syphilis, is a parasitic disease that is commonly contracted during illicit sexual intercourse. Conveyed by an infected man to his wife it frequently causes her to become sterile. Venereal diseases are disgenic agents of the first magnitude and of growing importance. The danger of acquiring them should be known to all young men. Society might well demand that before a marriage license is issued the man should present a certi¬ ficate, from a reputable physician, of freedom from them. Fortunately, nature protects most of her best blood from these diseases; for the acts that lead to them are repugnant to strictly normal persons; and the sober-minded young women who have had a fair opportunity to make a selec¬ tion of a consort are not attracted by the kind of men who are most prone to sex-immorality.

2. The Need of Eugenics

The human babies born each year constitute the world’s most valuable crop. Taking the population of the globe to be one and one-half billion, probably about 50 million children are born each year. In the continental United States with over 90 million souls probably 2x/2 million children are annually born. When we think of the influence of a single man in this country, of a Harriman, of an Edison, of a William James, the potentiality of these 2x/2 million annually can be dimly conceived as beyond computation. But for better or worse this potentiality is far from being

ITS NATURE, IMPORTANCE AND AIMS 3

realized. Nearly half a million of these infants die before they attain the age of one year, and half of all are dead be¬ fore they reach their 23rd year before they have had much chance to affect the world one way or another. How¬ ever, were only one and a quarter million of the children born each year in the United States destined to play an important part for the nation and humanity we could look with equanimity on the result. But alas ! only a small part of this army will be fully effective in rendering productive our three million square miles of territory, in otherwise utilizing the unparalleled natural resources of the country, and in forming a united, altruistic, God-serving, law-abiding, effective and productive nation, leading the remaining 93 per cent of the globe’s population to higher ideals. On the contrary, of the 1200 thousand who reach full maturity each year 40 thousand will be ineffective through temporary sickness, 4 to 5 thousand will be segregated in the care of institutions, unknown thousands will be kept in poverty through mental deficiency, other thousands will be the cause of social disorder and still other thousands will be required to tend and control the weak and unruly. We may estimate at not far from 100 thousand, or 8 per cent, the number of the non-productive or only slightly produc¬ tive, and probably this proportion would hold for the 600 thousand males considered by themselves. The great mass of the yearly increment, say 550 thousand males, constitute a body of solid, intelligent workers of one sort and another, engaged in occupations that require, in the different cases, various degrees of intelligence but are none the less valuable in the progress of humanity, Of course, in these gainful occupations the men are assisted by a large number of their sisters, but four-fifths of the women are still engaged in the no less useful work of home-making. The ineffectiveness of 6 to 8 per cent of the males and the

4 HEREDITY IN RELATION TO EUGENICS

probable slow tendency of this proportion to increase is deserving of serious attention.

It is a reproach to our intelligence that we as a people, proud in other respects of our control of nature, should have to support about half a million insane, feeble-minded, epileptic, blind and deaf, 80,000 prisoners and 100,000 paupers at a cost of over 100 million dollars per year. A new plague that rendered four per cent of our population, chiefly at the most productive age, not merely incompetent but a burden costing 100 million dollars yearly to support, would instantly attract universal attention. But we have become so used to crime, disease and degeneracy that we take them as necessary evils. That they were so in the world’s ignorance is granted; that they must remain so is denied.

3. The General Procedure in Applied Eugenics

The general program of the eugenist is clear it is to improve the race by inducing young people to make a more reasonable selection of marriage mates; to fall in love in¬ telligently. It also includes the control by the state of the propagation of the mentally incompetent. It does not imply destruction of the unfit either before or after birth. It certainly has only disgust for the free love propaganda that some ill-balanced persons have sought to attach to the name. Rather it trusts to that good sense with which the majority of people are possessed and believes that in the life of such there comes a time when they realize that they are drifting toward marriage and stop to consider if the contemplated union will result in healthful, mentally well-endowed offspring. At present there are few facts so generally known that they will help such persons in their inquiry. It is the province of the new science of eugenics to study the laws of inheritance of human traits and, as

ITS NATURE, IMPORTANCE AND AIMS

these laws are ascertained, to make them known. There is no doubt that when such laws are clearly formulated many certainly unfit matings will be avoided and other fit matings that have been shunned through false scruples will be happily contracted.

CHAPTER II

THE METHOD OF EUGENICS 1. Unit Characters and their Combination

When we look among our acquaintances we are struck by their diversity in physical, mental, and moral traits. Some of them have black hair, others brown, yellow, flaxen, or red. The eyes may be either blue, green, or brown; the hair straight or curly; noses long, short, narrow, broad, straight, aquiline, or pug. They may be liable to colds or resistant; with weak digestion or strong. The hearing may be quick or dull, sight keen or poor, mathematical ability great or small. The disposition may be cheerful or mel¬ ancholic; they may be selfish or altruistic, conscientious or liable to shirk. It is just the fact of diversity of character¬ istics of people that gives the basis for the belief in the practicability of improving the qualities of the “human harvest.” For these characteristics are inheritable, they are independent of each other, and they may be combined in any desirable mosaic.

The method of inheritance of these characteristics is not always so simple as might be anticipated. Extensive studies of heredity have, of late years, led to a more precise knowledge of the facts. The element of inheritance is not the individual as a whole nor even, in many cases, the traits as they are commonly recognized but, on the con¬ trary, certain unit characters. What are, indeed, units in inheritance and what are complexes it is not always easy

6

THE METHOD OF EUGENICS

7

to determine and it can be determined only by the results of breeding. To get at the facts it is necessary to study the progeny of human marriages. Now marriage can be and is looked at from many points of view. In novels, as the climax of human courtship; in law, largely as a union of two lines of property-descent; in society, as fixing a certain status ; but in eugenics, which considers its biological aspect, marriage is an experiment in breeding; and the children, in their varied combinations of characters, give the result of the experiment. That marriage should still be only an experiment in breeding, while the breeding of many animals and plants has been reduced to a science, is ground for reproach. Surely the human product is su¬ perior to that of poultry; and as we may now predict with precision the characters of the offspring of a particular pair of pedigreed poultry so may it sometime be with man. As we now know how to make almost any desired combina¬ tion of the characters of guinea-pigs, chickens, wheats, and cottons so may we hope to do with man.

At present, matings, even among cultured people, seem to be made at haphazard. Nevertheless there is some evi¬ dence of a crude selection in peoples of all stations. Even savages have a strong sense of personal beauty and a selec¬ tion of marriage mates is influenced by this fact, as Darwin has shown. It is, indeed, for the purpose of adding to their personal attractiveness that savage women or men tattoo the skin, bind up various parts of the body including the feet, and insert ornaments into lips, nose and ears. Among civilized peoples personal beauty still plays a part in selec¬ tive mating. If, as is sometimes alleged, large hips in the female are an attraction, then such a preference has the eugenic result that it tends to make easy the birth of large, well-developed babies, since there is probably a correlation between the spread of the iliac bones of the pelvis and the

8 HEREDITY IN RELATION TO EUGENICS

size of the space between the pelvic bones through which the child must pass. Even a selection on the ground of social position and wealth has a rough eugenic value since success means the presence of certain effective traits in the stock. The general idea of marrying health, wealth, and wisdom is a rough eugenic ideal. A curious antipathy is that of red haired persons of opposite sex for each other. Among thousands of matings that I have considered I have found only two cases where both husband and wife are red headed, and I am assured by red haired persons that the antipathy exists. If, as is sometimes alleged, red hair is frequently associated with a condition of nervous irri¬ tability this is an eugenic antipathy.

In so far as young men and women are left free to select their own marriage mates the widest possible acquaintance with different sorts of people, to increase the amplitude of selection, is evidently desirable. This is the great argument for coeducation of the sexes both at school and college, that they may increase the range of their experience with people and gain more discrimination in selection. The custom that prevails in America and England of free selec¬ tion of mates makes the more necessary the proper in¬ struction of young people in the principles of eugenical matings.

The theory of independent unit characters has an im¬ portant bearing upon our classifications of human beings and shows how essentially vague and even false in con¬ ception these classifications are. A large part of the time and expense of maintaining the courts is due to this anti¬ quated classification with its tacit assumption that each class stands as a type of men. Note the extended discus¬ sions in courts as to whether A belongs to the white race or to the black race, or whether B is feeble-minded or not. Usually they avoid, as if by intention, the fundamental

THE METHOD OF EUGENICS

9

question of definition, and if experts be called in to give a definition the situation is rendered only worse. Thus one expert will define a feeble-minded person as one incapable of protecting his life against the ordinary hazards of civili¬ zation, but this is very vague and the test is constantly changing. For a person may be quick-witted enough to avoid being run over by a horse and carriage but not quick enough to escape an automobile. A second expert will define a feeble-minded person as one who cannot meet all (save two) of the Binet test for three years below his own; if he fail in one only he is no longer feeble-minded. But this definition seems to me socially insufficient just because there are moral imbeciles who can answer all but the moral question for their proper age. Every attempt to classify persons into a limited number of mental categories ends unsatisfactorily.

The facts seem to be rather that no person possesses all of the thousands of unit traits that are possible and that are known in the species. Some of these .traits we are better off without but the lack of others is a serious handicap. If we place in the feeble-minded class every person who lacks any known mental trait we extend it to include practically all persons. If we place there only those who lack some trait desirable in social life, again our class is too inclusive. Perhaps the best definition would be: “deficient in some socially important trait” and then the class would include (as perhaps it should) also the sexually immoral, the crim¬ inalistic, those who cannot control their use of narcotics, those who habitually tell lies by preference, and those who run away from school or home. If from the term feeble¬ minded” we exclude the sexually immoral, the criminal¬ istic, and the narcotics such a restriction carried out into practice would greatly reduce the population of institutions for that class. Thus one sees that a full and free recogni-

10 HEREDITY IN RELATION TO EUGENICS

tion of the theory of unit characters in its application to man opens up -large social, legal and administrative ques¬ tions and leads us in the interests of truth, to avoid classify¬ ing persons and to consider rather their traits.

2. The Mechanism of the Inheritance of Characteristics

That traits are inherited has been known since man be¬ came a sentient being. That children are dissimilar com¬ binations of characteristics has long been recognized. That characteristics have a development in the child is equally obvious; but the mechanism by which they are transmitted in the germ plasm has become known only in recent years.

We know that the development of the child is started by the union of two small portions of the germ plasm the egg from the mother’s side of the house and the sperm from the father’s. We know that the fertilized egg does not contain the organs of the adult and yet it is definitely destined to produce them as though they were there in miniature. The different unit characters, though absent, must be represented in some way; not necessarily each organ by a particle but, in general, the resulting characteristics are determined by chemical substances in the fertilized egg. It is because of certain chemical and physical differences in two fertilized eggs that one develops into an ox and the other into a man. The differences may be called determiners.

Determiners are located, then, in the germ cells, and recent studies indicate a considerable probability that they are to be more precisely located in the nucleus and even in the chromatic material of the nucleus. To make this clear a series of diagrams will be necessary.

Figure 1 is a diagram of a cell showing the central nucleus in which runs a deeply staining network the chromatin. In the division of a cell into two similar daughter cells the

11

THE METHOD OF EUGENICS

most striking fact is the exact division of the chromatin (Fig. 2). We know enough to say that the nucleus is the center of the cell’s activity and for reasons that we shall see immediately it is probable that the chromatin is the most active portion of the nucleus.

Attraction-sphere enclosing two centrosomes

Nu- . cleus I

l

Plasmo- some or true nucle¬ olus

Chromatin-

network

Linin-net-

work

Karyosome, net-knot, or chromatin- nucleolus

Plastids lying in the cytoplasm

Vacuole

Passive bodies (metaplasm or paraplasm) sus¬ pended in the cytoplasmic meshwork

Fig. 1. Diagram cf a cell. Its basis consists of a meshwork containing numerous minute granules ( microsomes ) and traversing a transparent ground substance. From E. B. Wilson: “The Cell in Development and Inheritance.”

The fertilization of the egg (Fig. 3) brings together de¬ terminers from two germ plasms and we know that, on the whole, the two germ cells play an equal role in carrying determiners. Now the germ cells are of very different size in the female (egg) and the male (sperm). Even the nuclei are different; but the amount of chromatic substance is the same. Hence it seems probable that the chromatic substance is the carrier of the equal determiners.

But if determiners from the male are added to those from the female in fertilization it would seem necessary

12 HEREDITY IN RELATION TO EUGENICS

Fig. 2. Diagrams showing a series of stages in the process of division of the chromosomes during cell division. A. Resting cell in which the chromatic material lies (apparently) scattered through the nucleus: at c is a pair of recently divided central bodies ( centrosomes ) which come to be the centers of the forces that separate the chromosomes. B. The chromatin has fallen into the form of a thick ribbon or sausage-like body, outside of which lies a dark body which is called the “nucleolus.” The centrosomes are moving apart. C. The centrosomes now lie far apart and the thin membrane around the nucleus is beginning to disappear a process completed in D, where a “spindle” is seen lying between the two centrosomes. The chromosomes are beginning to move under the influence of the new forces centered at the centrosomes. E. A later phase in which changes of two sorts are taking place in the chromosomes; first, they are moving to an equatorial position between the two poles, and, secondly, they show their double nature by virtue of which the subsequent

THE METHOD OF EUGENICS

13

that the number ot these determiners should double in every succeeding generation. There must be some special mechanism to prevent this result. An appropriate mechan¬ ism is, indeed, ready and had been seen and studied long before its significance was understood; this is the elimina-

Fig. 3. Three stages in the fertilization of the egg of a marine ringed worm ( Thalassema ). As seen in thin dyed sections. A. At the top of the egg there is occurring a division of the chromosomes that constitutes the ripening or “maturation” of the egg, illustrated in greater detail in Fig. 4. At the bot¬ tom a sperm cell (cf) has entered the egg and is penetrating through it toward its center. B. The nucleus of the egg is now returning toward the center to meet that of the sperm. C. The egg and sperm nuclei are now in contact; henceforth they work in unison; fertilization is completed. After Griffin from E. B. Wilson: “The Cell in Development and Inheritance.”

tion from both the immature egg and the immature sperm of half of the chromatic material (Fig. 4). Thus if the im¬ mature sex-cell contains four chromatic bodies (chrom¬

osomes) each mature sex-cell will contain only two chromo¬ somes. Moreover, each of the chromosomes in the im¬ mature sex-cell is double; one half having originated long

before in its maternal germ plasm and the other half in its paternal germ plasm. The mechanism for maturation is

process of splitting takes place. F . The processes just preceding chromosome division are now completed; the activity of the centers is at its height; the chromosomes now constitute an “equatorial plate,” e. p. G. 1 he chromosomes at the equatorial plate are now beginning to move apart. II. The separation of the chromosomes is continuing and in I is completed; meanwhile the ac¬ tivity at the centers has declined and division of the body of the cell is begin¬ ning J. Division of the cell completed; the nuclei and centrosomes at the condition with which we started at A. From E. B. Wilson: “The Cell in Development and Inheritance.”

14 HEREDITY IN RELATION TO EUGENICS

Fig. 4. Diagrams illustrating the process of reduction of the chromosomes by which half of the chromatic material is eliminated from the sex-cell. A. The germ cell is beginning its penultimate division there are four chromosomes but each of them has already begun to divide to go to their respective poles, as seen at B. C. The last division is taking place, but the four chromosomes do not lie side by side in the equatorial plate as in A, but they unite in two pairs and, in the division, the elements of these pairs are sundered again. Thus out of the original cell four ripe sperm-cells (D) each with only two chromo¬ somes arise. From E. B. Wilson: “The Cell in Development and Inheritance.”

such that either the paternal or maternal component of any chromosome is eliminated in the process, but not both. (Fig. 5). Beyond the condition that one half