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Heredity and eugenics

HEREDITY AND EUGENICS

THE UNIVERSITY OF CHICAGO PRESS
CHICAGO, ILLINOIS

gents

THE BAKER & TAYLOR COMPANY
NEW YORE

THE OAMBRIDGE UNIVERSITY PRESS
LONDON AND EDINBURGH

HEREDITY AND EUGENICS

A COURSE OF LECTURES SUMMARIZING RECENT ADVANCES IN KNOWLEDGE
IN VARIATION, HEREDITY, AND EVOLUTION AND ITS RELATION
TO PLANT, ANIMAL, AND HUMAN IMPROVE-
MENT AND WELFARE

BY

WILLIAM ERNEST CASTLE
JOHN MERLE COULTER
CHARLES BENEDICT DAVENPORT
EDWARD MURRAY EAST
WILLIAM LAWRENCE TOWER

THE UNIVERSITY OF CHICAGO PRESS
CHICAGO, ILLINOIS

COPYRIGHT 1912 By

Tue UNIVERSITY OF CHICAGO
All Rights Reserved

Published June 1912
Second Impression January I913

Composed and Printed By
The University of Chicago Press
Chicago, Mlinois, U.S.A.

PREFACE

During the summer of rg11, a course of lectures on
heredity and allied topics was given at the University of
Chicago, under the auspices of the biological departments.
The purpose of the course was to present the recent develop-
ments of knowledge in reference to variation, heredity, and
evolution, and the application of this new knowledge to
plant, animal, and human development and improvement.

The lectures were not intended for those trained in
biology, but for a general university audience, interested
in the progress of genetics as a matter of information rather
than of study. The lecturers, therefore, did not address
themselves to their colleagues, and did not attempt to
include any considerable amount of new material. It is
believed that a much larger audience than the one originally
addressed might be interested in this summary of results
in one of the important and recently cultivated fields of
biology, and therefore this volume has been published.
It is hoped that it may perform a service not only for those
interested in biology as a field outside their own experience,
but also for those biologists whose work deals with other
phases of biology.

The lectures were given by five lecturers, with no oppor-
tunity to relate the lectures to one another other than as
suggested by the assigned titles. It is inevitable that there
should be more or less overlapping of statements, and no
attempt has been made to avoid this. Each lecture,
therefore, is complete in itself, as it was delivered.

Vv

vil Preface

No attempt has been made to include the whole of the
fields represented by the general topics. The plan was to
select certain representative investigators to speak of their
work. Four such investigators were selected, the mission
of the fifth lecturer being to give the elementary information
(chaps. 1 and ii) necessary for an audience untrained in biology,
and thus to prepare the way for the more special topics.

It is hoped that similar series of lectures in other fields
of biology will be given during successive summers, and
that the present volume may be the first of a series which will
represent the most significant aspects of current biological
investigation.

J. M. CouLtTEerR
fale at By 0 2 83
W. L. Tower

CHAPTER

I

E

III.
IV.

VI.

VI.

VIII.

IX.

TABLE OF CONTENTS

RECENT DEVELOPMENTS IN HEREDITY AND EVOLUTION:
GENERAL INTRODUCTION

Tue PuysicaL Basis orf HEREDITY AND EVOLUTION
FROM THE CYTOLOGICAL STANDPOINT

JouNn Merte Courter, Professor and Head of the
Department of Botany, the University of Chicago

Tue Metuop or EVOLUTION

HEREDITY AND SEX

WiLtiaAmM ERNEST CastLe, Professor of Zodlogy, Har-
vard University

INHERITANCE IN THE HIGHER PLANTS

THE APPLICATION OF BIOLOGICAL PRINCIPLES TO PLANT
BREEDING

Epwarp Murray East, Assistant Professor of Experi-
mental Plant Morphology, Harvard University

RECENT ADVANCES AND THE PRESENT STATE OF KNOWL-
EDGE CONCERNING THE MODIFICATION OF THE GER-
MINAL CONSTITUTION OF ORGANISMS BY EXPERIMENTAL
PROCESSES
Witt1am LAWRENCE TowWER, Associate Professor of
Zodélogy, the University of Chicago

Tue INHERITANCE OF PHYSICAL AND MENTAL TRAITS
or MAN AND THEIR APPLICATION TO EUGENICS
Tue GEOGRAPHY OF MAN IN RELATION TO EUGENICS
CuHaRLES BENEDICT DAVENPORT, Station for Experimen-
tal Evolution, Carnegie Institution of Washington
INDEX

vil

PAGE

22

39
62

83

113

141

269
289

313

JOHN MERLE COULTER

Professor and Head of the Department of Botany
The University of Chicago

CHAPTER I

RECENT DEVELOPMENTS IN HEREDITY AND
EVOLUTION: GENERAL INTRODUCTION

This series of lectures is intended to present, in outline,
the recent development of knowledge in reference to heredity
and evolution. These subjects have to do, not only with
the most fundamental conceptions of biology, but they have
come to be of immense practical importance in animal and
plant breeding. From every aspect, therefore, they appeal
to all persons intelligent enough to be interested in the
progress of knowledge and in human welfare. At the same
time, it is recognized that most people are denied the oppor-
tunity of knowing the progress that has been made in these
subjects, through lack of biological training or lack of time.
To them the suggestions of progress have come chiefly
through ephemeral and often misleading publications.

It is the purpose of this series, therefore, to present this
information in such a form that it can be appreciated by
those who have no special training in biological work; in short,
to interpret the significant results of recent investigations.

Before presenting the recent developments in the inves-
tigation of heredity and evolution, it is essential to provide
a historical background, for nothing is more obvious than
that the work of today has evolved gradually from all the
work of the past. It should be understood, also, that the
subject is so vast in scope and in work that to outline it in
a few lectures will require the most rigid selection of material,
a selection so rigid that students of the subject will be able
to point out glaring omissions.

3

4 Heredity and Eugenics

If rigid selection is necessary in presenting the recent
work, it must be still more rigid in sketching the historical
background, with its enormous literature, stretching through
many years. Probably no two biologists would put the
same details into the background, but probably all of them
would give the background the same general aspect; for
it is more of an atmosphere than detail that is needed. It
will be an aid to understanding and to memory if this
sketch is broken up into distinct topics, if it be understood
clearly that there are no such natural lines of cleavage in
the subject.

I. THE CONCEPTION OF EVOLUTION

Those who know of the theory of evolution only in a
superficial way, as a thing heard of rather than understood,
almost invariably associate it with some man who stands
to them as its author. In my own experience, I have
encountered a widespread conviction that Darwin is respon-
sible for the theory of organic evolution. The fact is that
the conception of evolution, both inorganic and organic, is
as old as our record of man’s thought, and therefore no one
is responsible for it. It is the common property of the
human race.

However, a sharp distinction must be made between the
speculative stage of evolution and the observational stage.
The former is imaginative or philosophical, and could not
establish evolution as a fact; the latter is scientific, and has
e:tablished evolution as a fact. In a real sense, therefore,
organic evolution as a definite working principle is compara-
tively modern, being but little more than one hundred
years old.

Recent Developments in Heredity and Evolution 5

2. THE FACT OF EVOLUTION

It may be helpful to indicate some of the things that
began to open the eyes of thinking men and finally compelled
them to accept organic evolution as a fact.

1. The growing proof that the inorganic world had been
formed by a process of slow evolution rather than by a
series of miraculous catastrophes, compelled the suggestion
that the organic world may have developed in the same
gradual way by natural processes.

2. The observed intergrading of species, frequently so
complete as to make distinct boundaries for species impos-
sible, strongly suggested the passing of one into the other.
Dr. Asa Gray once remarked that he did not believe there
are any species of North American asters, although he had
been studying them for twenty years. Of course this was
an expression of despair rather than of belief, but it illus-
trates the situation. Botanists for a long time emphasized
the boundaries of species by preserving in their herbaria
what they called ‘‘typical specimens” and discarding the
intergrades, so that in turning over the sheets of a herbarium
the species looked quite distinct; but any excursion into
the field brought trouble.

3. Observations began to multiply showing that plants
and animals are often able to respond to changed con-
ditions and change their own form or structure. This
was called the power of “adaptation,” and it has been
a most persistent idea. The fact of change was evident,
but its explanation has been outgrown. But taking it
as a fact, it was evident that the small changes observed
would suggest the possibility of indefinitely extended
changes.

6 Heredity and Eugenics

4. More intimate knowledge of the structure of plant
and animal bodies revealed what were called “‘ rudimentary ”’
structures, which are quite evidently abandoned structures.
This suggested at once that they were functioning structures
in the ancestral forms. Even man, and perhaps man most
of all, was recognized as being a walking museum of antiquity.

5. Then the life panorama of the geological record
began to be unrolled; and it became clear that a fauna and
a flora totally unlike that of today existed in the earliest
periods; that as one approached the later records, resem-
blances began to appear; and that insensibly the fauna
and flora of the ancient world merged into those of today.
This was historical evidence of tremendous weight in favor
of the fact of a gradual organic evolution.

6. Soon what is called embryology began to be studied,
and plants and animals were traced, stage by stage, from
the egg to the adult form. In the course of this develop-
ment resemblances to other forms appeared, which had
disappeared when the adult stage was reached. And so
the idea developed that here were glimpses of earlier con-
nections, and it became formulated in the well-worn state-
ment that the history of the individual repeats the history
of the race, a theory labeled “recapitulation.”

7. Men’s eyes also began to be opened to the fact that
great changes had been wrought in plants by cultivation,
and in animals by domestication; so great in many cases that
the wild originals could not be recognized with certainty.
Later, Darwin called this ‘‘an experiment upon a gigantic
scale,” but it was an experiment unconsciously performed.
At least it proved that the operations of man could modify
plants and animals, and modify them so much that resem-
blances to the wild originals would be obscured.

Recent Developments in Heredity and Evolution 7

The seven categories of facts thus indicated, and others
that might be added to them, will explain why a number
of scientific men were so impressed by the idea that organic
evolution is a fact, that they thought it important to
search for an explanation of the process.

3. THE EXPLANATION OF EVOLUTION

To accept organic evolution as a fact, and to explain
it as a process are two very different things, and must be
kept clearly distinct. The failure to distinguish them has
led recently to much confusion in popular statement and
belief. For example, the more exact work of recent years
has developed a considerable body of criticism against
Darwin’s theory of natural selection. To those who thought
of the theory of organic evolution as belonging to Darwin,
these criticisms seemed to indicate that belief in organic
evolution was tottering; when in fact, if any belief was
tottering, it was a belief in natural selection as a sufficient
explanation of the process of evolution. Darwin’s explana-
tion, Lamarck’s explanation, every explanation hitherto
proposed, may be found inadequate, and still organic
evolution will remain to be explained. It must be remem-
bered that the work of biologists has been to explain the
fact of organic evolution, not to propose it as an idea; and
the destruction of no explanation can weaken the fact.

A single address does not permit the mention of all the
proposed explanations of organic evolution, but a few domi-
nating ones may be selected as illustrations. The selection
is made with a full appreciation of the fact that profes-
sional biologists may think that others should be included.

It is important to distinguish between the two methods
of attacking the problem. The earlier method, and the

8 Heredity and Eugenics

one that prevailed for nearly one hundred years, was obser-
vational. Series of intergrading plants and animals were
observed, and by comparing them it was inferred that they
represented the series of transformations that had occurred
actually in nature. This has remained the only possible
method for the paleontologist, and he also has the advantage
_ of dealing with series of enormous length. It is to be
expected, therefore, that the paleontologist will be impressed
most strongly by those explanations of evolution which
have been derived from observation and comparison.

The later method of attacking the problem, a method
that has developed with great rapidity during the last
decade, is experimental. Plants and animals are taken in
hand and are made to show their possibilities.

It should be kept in mind that the problem is to explain
how one species can produce another. The study of organic
evolution deals only with the succession of forms, with the
production of new forms by previously existing ones. It
has nothing to say concerning origins. How the numerous
series of living forms may have originated is certainly
beyond the reach of biological science as yet. When one
goes beyond the observed changes, and tries to trace the
successions back to their source, he is in a region of specu-
lation, and outside the boundaries of science. One may
stand beside a great stream and discover that its waters
are moving; he also recognizes the direction of the move-
ment; but he can know nothing of the distant sources
of the stream, for he sees only a very small section. So
the scientific recognition of organic evolution simply
observes the movement and its direction. The sources are
far too distant for observation, and the possibilities are
too numerous for profitable speculation. It is evident that

Recent Developments in Heredity and Evolution 9

people in general are more interested in speculation than
in plain facts; and they are so interested in such speculations
as the origin of life and the origin of man that they come
to believe that these speculations belong to the scientific
study of organic evolution. But we are simply collecting
the facts of change and trying to discover the causes and
processes of change in the plants and animals that can come
under our observation. We can thus discover laws of
evolution, just as we discover the law of gravitation, by
observing them in operation. Of course the ultimate
questions continually suggest themselves, but it must not
be thought that any proposed answers to them are a part
of biological science.

1. Environment.—The first attempt at what might be
called a scientific explanation of organic evolution, because
based upon observation, was that it is caused by changes in
environment. This explanation began to take definite form
during the last decade of the eighteenth century, in the
writings of such observers as Erasmus Darwin of England,
St. Hilaire of France, and Goethe of Germany. Environ-
ment is a term quite variable in its biological application,
but we do not need to discuss it in this connection. These
older observers saw changes occurring in plants and animals
(especially the latter), in response to changes in seasons,
in exposure, in climate, etc.; and their picture of the process
of evolution was that plants and animals are plastic organ-
isms that are being molded by their environment. The
environment and the molding were not analyzed, but
thought of in a very superficial sense; so that it was not
long before it was recognized that the changes thus induced
are too superficial and ephemeral to furnish an adequate
explanation of evolution. But it must not be forgotten

10 Heredily and Eugenics

that environment, even in its superficial sense, is a very
real factor, and has played its part in every evolutionary
theory since.

2. Use and disuse.—In the early part of the nineteenth
century, the first substantial explanation of organic evolu-
tion was proposed. Its author was Lamarck, and the theory
has become styled Lamarckism or Lamarckianism, but its
author called it ‘‘appetency,’’ or the doctrine of desires.
It is more intelligible to the uninformed as the effect of use
and disuse. This explanation has been a conspicuous part
of evolutionary doctrine ever since, and in modified form is
known today as neo-Lamarckianism. The conception is
simple enough and has a basis of facts. It is well known,
for example, that use develops a muscle, and that disuse
deteriorates it, a deterioration that may reach as far as
inability to function. If this effect of use and disuse be
applicable to all organs and regions of the body, and certain
conditions of living were to change, demanding the use of
structures that had not been called upon to do so much
service before, and also excusing from such constant service
structures that had been very active before, one might
imagine changes taking place in the greater development of
certain structures and the less development of others. In
other words, change in the environment means change in the
demands on the structures of plants and animals, and these
demands are met by the active exertion of the organism.

A well-known illustration used by Lamarck will serve
our purpose. A grazing animal, with an ordinary neck,
is placed in conditions that demand feeding upon the foliage
of trees. The continuous use of the neck in stretching
would cause it to increase somewhat in length. This
slight increase in length would be transmitted to the next

Recent Developments in Heredity and Evolution II

generation, which in turn would add to it, until a number
of generations would succeed in developing the exaggerated
neck of the giraffe.

This illustration makes clear the factors relied upon by
Lamarck, namely, the effect of use demanded by changed
conditions, and the transmission of the changes from parent
to offspring. His own name, “appetency,” sought to ex-
press the idea of striving to satisfy a desire; but, as might
have been expected, it was not understood by most of the
people of his day, and lent itself admirably to all sorts of
caricature.

The changes in structure brought about during the life
of an individual are spoken of as “acquired characters,”’
and Lamarck’s explanation of the evolutionary process
would be impossible if acquired characters are not trans-
mitted from parent to offspring. The present consensus of
opinion seems to be that such acquired characters as
Lamarck had in mind are not transmissible; but the whole
subject of the transmission of acquired characters is more
a matter of definition than anything else.

3. Natural selection—It was the explanation offered by
Charles Darwin, however, that proved to be the most
epoch-making theory in the history of biological science.
He called it ‘‘natural selection,” and it has been a domi-
nating conception for fifty years. With the Darwin
centennial celebrations only two years old, and with the
flood of literature that accompanied and followed them,
no one interested in the subject of evolution can be ignorant
of the meaning of natural selection, or of the revolution in
thought and method brought about by its presentation in
Darwin’s Origin of Species. While Lamarck’s conception
was based upon extensive observation, and therefore was

12 Heredity and Eugenics

reached in a thoroughly scientific way, Darwin’s conception
was based upon an amount and range of observation hitherto
unapproached; so that if Lamarck’s approach was scien-
tific, Darwin’s was still more scientific. In fact, Darwin’s
announcement came at a psychological moment, which
enormously reinforced his message; and this is not detract-
ing in the least from the power and beauty of its presenta-
tion. Whether Darwin’s explanation stands or falls, his
supreme contribution must be regarded as the introduction
of a point of view and a method of attack that not only
ushered in modern biology, but also revolutionized thought
in general.

Natural selection is too familiar to need extended expla-
nation. The ratio of increase of organisms, leading to
over-production and a struggle for existence, resulting in
the survival of the fittest, is a series of exceedingly familiar
phrases, not all of which should be attributed to Darwin.
That plants and animals can be led along in any desired
direction was proved by experimental evidence obtained
from the operations of plant and animal breeders; and since
this guidance of plants and animals by man was by means
of selection, it was most appropriate to call the guidance
by nature ‘‘natural selection.”’

The most significant fact connected with this theory
remains to be mentioned, and that is the fact of variation.
Nothing is more clear than that any machinery of evolution
must depend upon this fact. Darwin greatly enlarged the
horizon of our knowledge in reference to variation. It is
variation that gives rise to individuality among plants and
animals, so that no two plants or animals are exactly alike.
We have accustomed ourselves to individuality among
human beings, for we have been trained to note the dis-

Recent Developments in Heredity and Evolution 13

tinguishing marks. But this same individuality is no less
true for all animals and plants. In heredity, therefore,
there is transmitted not only a likeness to the parent, but
also an unlikeness, and this unlikeness constitutes indi-
viduality, a certain amount of variation from the parent.

Darwin’s conception was that nature selects from
among these varying individuals; that the means of selec-
tion is the competition that results from over-production;
that the better adapted individuals would naturally be
selected for survival; that their better adaptations, which
mean their individual peculiarities, would be transmitted
to their offspring; and that such selection, continued genera-
tion after generation, would so emphasize and increase the
favored variations that the old species boundary would be
crossed and a new species established. In other words,
small variations would be built up into larger ones, and
presently they would become too large to be included within
the boundary of the old species.

Of course, objections have been raised to the theory of
natural selection as an adequate explanation of the origin
of species. There can be no doubt but that there is selec-
tion in nature, in the sense that not all the forms produced
survive; but many believe that this cannot change forms
enough to be regarded as new species; that any selection
thus made cannot be on the basis of any “life-and-death”’
advantage of structure that one individual has over another;
and that the variations thus used are only the so-called
“fluctuating variations’? which have nothing definite in
them as to direction or amount.

4. Mutation—We come now to the work of the last
decade, which is characterized by the rapid development
of the study of evolution by using experimental methods.

14 Heredity and Eugenics

Perhaps the most influential work to enforce the experi-
mental method was that of DeVries, in developing his
theory of mutation. His great contribution, therefore,
must not be regarded as offering mutation as an explana-
tion of the origin of species, for that explanation may not
stand, but as establishing, or at least powerfully helping to
establish, the study of evolution upon an experimental basis.

The mutation theory needs no extended explanation,
for the current literature of organic evolution is full of it.
The long series of cultures of Oenothera, under rigid control
and in large numbers, are familiar. The appearance, in
relatively very small numbers, of widely different indi-
viduals, which “‘came true”’ in subsequent generations, led
to the inference that new species were appearing under
observation, suddenly produced by the parent form, fully
equipped as species, without any intermediate stages or
any building up by selection. It should be noted that this
does not banish natural selection as a factor in evolution,
but assigns to it a new role, which is not to produce species,
but to select among those already produced.

The study of mutations is one of the vigorous phases of
experimental work today, and some of the results will be
presented in the subsequent chapters. Objections to the
theory have developed, as must be the case in all theories.
There are questions as to the extent of mutation as a process
going on among plants and animals; as to its reliability in
producing species; as to whether mutants are really new
forms, or only old ones derived from a splitting hybrid
parent. It is such questions, and others like them, that
experimental work today is trying to answer.

5. Orthogenesis.—The barest kind of evolutionary back-
ground would be inadequate without a mention of ortho-

Recent Developments in Heredity and Evolution 15

genesis. The variations utilized in the preceding explana-
tions, both the smaller ones used by natural selection and
the larger ones used by mutation, occur in every direction
from the parent form, the successful direction being deter-
mined by natural selection. This has been called indeter-
minate variation. In tracing the evolution of great groups,
however, it becomes clear that the most important varia-
tions occur in certain definite directions, which have been
maintained persistently throughout all possible changes of
condition. For example, the history of such a group as
gymnosperms shows a tendency to vary in certain definite
directions that has persisted from the early Paleozoic to
the present time. In other words, there is much to indicate
that while variation may be indeterminate, there are also
certain definite lines that persist. The origin of new forms,
whether by natural selection or mutation or neither, as the
result of a persistent determinate variation, is called ortho-
genesis. It certainly removes one of the greatest difficul-
ties in the way of natural selection, and that is the beginning
and development of a structure that can be of advantage
only when it is completed. It satisfies also the many
known cases of excessive development in certain directions,
a development that may be not only disadvantageous, but
even destructive. Even if determinate variation is accepted
as a fact, however, what determines the persistent variation ?
The answer to this question has resulted in many variations
of the theory of orthogenesis.

It should be noted that natural selection, mutation, and
orthogenesis are not mutually destructive. They all deal
with variations, and may all be operative in producing new
forms. Natural selection deals with small variations which
are in every direction; mutation with large variations which

10 Heredity and Eugenics

are in every direction; and orthogenesis with those small
or large and relatively few variations which for some reason
persist and increase from generation to generation and carry
forward the group as a whole.

4. BIOMETRY

When the idea of natural selection became dominant,
and new species were believed to have arisen by the accumu-
lation of small variations, which seemed to be indefinite
and fluctuating, a statistical method of attack began to be
developed, a method that has been named biometry. The
most conspicuous names that one meets in the literature of
biometry are Galton, the English pioneer in the exploitation
of the method; and Pearson, who has been largely instru-
mental in carrying it forward into its more advanced
mathematical stage.

It is a method that deals with groups or populations,
rather than with individuals, and its results present the
averages of variations. It is evident that an average
obtained from the measurements of a given character in a
series of individuals will depend upon the individuals
selected for measurement. Therefore, biometry demands
to an unusual degree the elimination of preconceived opin-
ions and the exercise of great judgment. It has become
so special and intricate a method that it can be followed,
with full understanding, only by those with special training;
so that any adequate illustration of it will be left to such of
the subsequent addresses as may have occasion to apply it.

A word can be said, however, concerning its use as an
instrument in the study of the processes of evolution.
Selecting any character or group of characters that are to
be measured or counted, and using a wisely selected range of

Recent Developments in Heredity and Evolution 17

material, biometry reveals the prevailing tendency, in
reference to these variations, in a group of individuals
representing a species, a tendency that could not be recog-
nized by the study of a single individual. Applying this
method to successive generations from this group of indi-
viduals, under experimental control, it can be discovered
whether the prevailing tendency in the expression of these
variations remains the same, continuing the species as
before; or shifts, modifying the species as a whole; or
splits up, giving rise to a second marked tendency, that
may mean presently two distinct species.

It is evident that such data can be very suggestive, but
that their limitations must be recognized. They are data
concerning successive populations, and show the average
result of individual variation as expressed in a population.
In other words, they present in concrete and somewhat
definite form the problems of variation and inheritance
that must be solved.

5. HEREDITY

It must have become evident, during the preceding
sketch of representative theories of evolution, that the
fundamental factor in the process is variation, and that the
essential and inevitable question behind all of these explana-
tions is the origin of variation. This brings us at once to
the problem of heredity, with its supposed processes for
transmitting what we call ‘“‘characters” from parent to
offspring. How is variation secured in this transmission ?
The earlier observers simply accepted variation as a fact,
and made no serious attempt to explain it.

The first attack upon this problem was the accumulation
of data in reference to the facts of heredity. To accumulate

18 Heredity and Eugenics

these facts in such numbers as to make any generaliza-
tion worthy, demands the culture through many generations,
under most rigid control, of the largest possible number of
plants and animals. This means long periods of time, great
patience, and many investigators. The number of investi-
gators is multiplying, the range of material is increasing,
and the period covered by some of the work has now been
sufficient to justify some presentation of the results.

Probably the most conspicuous working hypothesis
today, in connection with the collection and interpreta-
tion of the data of heredity, is the one called ‘‘ Mendel’s
law.”’ This is to be made a special theme in the course of
this series, but a brief statement in reference to it will
help the background and may prepare the way for the later
discussion. This Austrian monk, who worked in _ his
monastery garden during the middle of the last century,
left on record what is called a law of heredity. This record
was lost, so far as its influence was concerned, until
ten or fifteen years ago, when the modern movement in
experimental evolution began to be vigorous. Now the
Mendelians constitute a conspicuous biological cult, and
Mendelism has extended from its simple original state-
ment into a speculative philosophy, with conceptions of
unit-characters, dominance, ratios, etc., that the untrained
cannot follow.

The fundamental conception is simple enough. If two
different species are crossed, the result is a hybrid which
combines certain characters of both parents. When this
hybrid propagates, the progeny splits up into three sets:
one set resembling the hybrid parent; and the two other
sets resembling the parent forms that entered into the
hybrid. Mendel’s law is a statement of the definite ratio

Recent Developments in Heredity and Evolution 19

expressed by these three groups of forms derived from a
splitting hybrid. This means that in a series of genera-
tions initiated by a hybrid, approximately one-half of the
individuals of each generation will represent the hybrid
mixture, one-fourth of the individuals will represent one
of the pure forms that entered into the hybrid, and the
remaining fourth will represent the other pure form.

It should be understood that the use of hybrids in such
experimental work is simply a device to secure easy recog-
nition of the contributions of each parent to the progeny.
For example, if red and yellow races of corn are crossed, it
is very simple to recognize the color contribution of each
parent to the hybrid progeny, when it would be impossible
to separate the contribution of two yellow parents. The
inference is, that what is true of hybrids is true of forms
produced in the ordinary way, so that laws of heredity
obtained from a study of hybrids may be regarded as
laws of heredity in general. In one sense, every union of
parent forms is hybridizing, for each parent has its own
individuality.

One of the more subtle problems that has arisen in
connection with such investigations is the problem of sex
determination. In all organisms with sex differentiation,
progeny is produced by the fusion of male and female
sexual cells, and this progeny develops as distinct male
and female individuals. It is one thing to determine the
general structure of an organism by some law of heredity,
but a very different thing to determine why any individual
thus produced is sometimes male and sometimes female.

The work of today is not resting content with the patient
collection of the facts of heredity, with determining ratios
as expressions of laws, and with the end results of processes

20 Heredity and Eugenics

initiated under experimental control. There is keen search-
ing for cytological evidence; and the structure and behavior
of the sexual cells, through the whole process of their forma-
tion, during the act of fusion, and in the initiating activity
of the fertilized egg, are being subjected to all the scrutiny
that a developing technique can devise to discover the
mechanism of heredity. Moreover, cytological evidence is
being searched for not only to discover a possible physical
basis for heredity, which would mean actual material
machinery, but also to discover the possible relations of
chemical and physical factors to this most fundamental
and obscure process. It is believed that it must be a
response, in terms of chemistry and physics, by a living
material substance.

6. PRACTICAL APPLICATIONS

In a university atmosphere, the chief interest is probably
focused upon the attempt to reveal one of the so-called
“mysteries” of life, those mysteries which always invite
one to uncover them; but there is another aspect of these
problems worth considering. The experimental work that has
been done in the study of heredity and evolution has had a
very important bearing upon the practical handling of plants
and animals, including the human animal. The applica-
tions have been made to plants most extensively, and
methods of plant breeding have been revolutionized. The
recognition that commercially ‘‘pure seed” is an extensive
mixture of different types or strains, has led to their
separation, and has changed the clumsy and _ inefficient
method of mass culture to the definite and exact method of
pedigree culture. As a consequence, the number of forms
made available for culture has been multiplied enormously,

Recent Developments in Heredity and Evolution 21

having simply been discovered and pedigreed, without the
labor of continuous selection year after year, and without
the old inconstancy in the result. To reduce labor, to
multiply cultural forms, and to obtain constant results
in plant breeding are results of very large importance to
the material side of human welfare. Pedigree culture has
not only multiplied available forms, but it has begun to
be used most effectively in combating drought and disease,
the most dangerous enemies of cultivated plants. Drought-
resistant races are being developed from pedigreed stock,
and immunity to different diseases has been found to be
a transmissible character. When it is remembered that
drought-resistance not only insures crops over areas now
cultivated, but also secures an enormous extension of area
that can be cultivated; and that the annual losses from
plant diseases represent an enormous financial total; it
will be appreciated that the study of heredity and evolution,
with purely scientific purpose, incidentally has been enor-
mously profitable on the practical side.

I have sketched a background that will permit those who
follow to put their work in its setting without much loss
of time. The interest lies chiefly in the foreground that
they will develop, for it will represent the work of today.

CHAPTER II

THE PHYSICAL BASIS OF HEREDITY AND EVOLUTION
FROM THE CYTOLOGICAL STANDPOINT

Heredity involves not only the transmission of similarity
in structure, but also the transmission of dissimilarity.
Likeness means close relation to the parent forms; unlike-
ness means individuality. It is not generally appreciated
that individuality expresses itself just as certainly among
plants and animals as among human beings. We have
learned to recognize the marks of individuality among
human beings through long acquaintance, but we should
realize also that no two plants or animals are exactly alike.
It is this individuality that is called variation, and variation
is the basis of evolution. The phenomena of heredity
established as facts by series of cultures under rigid control,
however, must be recognized as the end results, between
which and the act of fertilization there extends a series of
unknown processes, with which as yet only scientific imagi-
nation deals.

The purpose of this chapter is to inquire whether there
is any physical basis for the transmission of like and unlike
characters, in the same sense that protoplasm was long ago
called ‘‘the physical basis of life.’ This phrase only means
that protoplasm is the material substance in which the
phenomena of life are manifested. Is there any substance
or structure by means of which the phenomena of heredity
manifest themselves ?

The answer to this question would be given more appro-
priately by some biologist who has made it the special

22

Physical Basis of Heredity and Evolution 23

subject of his investigations. This chapter, therefore,
must be regarded simply as the presentation of a teacher,
to explain a subject that belongs logically in the series.
Another restriction is that this presentation deals chiefly
with structures that are visible by means of laboratory
technique, and not with the results of experiment upon
these structures. A final restriction is that the statements
deal with plants, a limitation necessary to the writer, and
offset by the fact that the corresponding facts in animals
will be stated in one of the later chapters.

Some conception of what is meant by the power of repro-
duction will be useful. Among the simplest plants, every
cell has this power; in fact, some plants are so simple that
the adult body consists of a single cell. As plant bodies
came to be made up of numerous cells, some of them lost
the power of reproduction; and as the body became increas-
ingly complex, the number of cells retaining the power of
reproduction became relatively smaller. This means that
in the complex plant body, the relatively few reproductive
cells are not so much “‘cells set apart for this special func-
tion,” as cells that have not lost this primary power. The
specialized cells are not those that reproduce, but those
that cannot. The loss of reproductive power is usually
not complete, for most cells can reproduce their own kind,
even if they cannot reproduce the whole body.

This leads to a consideration of what is included in full
reproductive power. Without including confusing details,
it may be said that such reproduction as one has in mind
in connection with heredity involves four general things.
First, there is cell multiplication, the fertilized egg initiating
a series of cell divisions that may result in a multitude of
cells. It is evident, however, that a complex plant body is

24 Heredity and Eugenics

more than a multitude of similar cells. In the second place,
there is cell differentiation, groups of cells becoming different,
so that the various tissues, with their special functions, are
developed. In the third place, tissues must be organized
together into the structures called organs. In the last
place, the organs must be combined in making that total
organization called the individual. It is this far-reaching
directive influence that is the most baffling fact in connection
with heredity.

To obtain any impression of the supposed machinery of
heredity, it is necessary to know something of the structure
of a living cell. So far as material goes, such a cell is an
individualized mass of protoplasm. This protoplasm is
organized into a body known conveniently as the proto-
plast, which is the living body of the cell. In plants, the
protoplast usually constructs a cellulose wall about itself,
which has given rise to the impression that a cell is a walled
chamber containing protoplasm. In the plant cells which
have to do directly with heredity, however, namely the
reproductive cells, the cellulose wall is not formed, and
they are naked protoplasts. The protoplast is exceedingly
complex, as cytologists well know, and includes a variety
of organs. Conspicuous among these protoplasmic organs is
the nucleus, which is a more or less spherical body and usually
sharply limited from the rest of the protoplast, in which it
lies imbedded (Fig. 1). The remainder of the protoplasmic
material enters into the structure of the cytoplasm, another
organ or region of the protoplast constantly associated
with the nucleus. Every living cell contains a nucleus and
cytoplasm, and in addition there may be other protoplasmic
organs (Fig. 1), but the two mentioned are those that belong
to this discussion.

Physical Basis of Heredity and Evolution 25

As in the case of all organs, the cytoplasm and the nucleus
are associated with special functions. This does not mean
that each does a certain thing and nothing else, but that each
is conspicuous in connection with a certain kind of work.

Especially unsafe is it to
ascribe certain definite
functions to these organs of
the protoplast, because pro-
toplasm itself is so little
understood. In any event,
the cytoplasm seems to be
conspicuously associated
with the metabolic activi-
ties of the cell; and it is
certain that the nucleus is
conspicuously associated
with cell division. When
division occurs, and one
cell gives rise to two cells,
this process almost invari-
ably begins with the nu-
cleus, which may thus be
said to initiate cell division.
It must be understood
clearly that we are speak-
ing of visible changes in
structure, behind which and

Fic. 1.—Cells from a moss leaf: each
of the complete cells shows the well-
defined nucleus; since the leaf is green,
there are also numerous green protoplas-
mic organs (chloroplasts); the remaining
cranular-looking ground substance is the

cytoplasm.

accompanying which there are certainly numerous invisible
physical and chemical changes.

It is evident that the problem of heredity is involved
in the process of cell division, for through this process the
old cell transmits whatever determines the characters of

20 Heredity and Eugenics

the two new cells. In ordinary cell division, the imme-
diate transmission seems to be a similar structure, for the
new cells resemble the old one in all recognizable features.
In the differentiation of cells, however, certain cell divisions
involve the transmission of unlike characters.

This relation of the nucleus to cell division, and of cell
division to heredity, has focused the attention of cytolo-
gists upon the structure and behavior of the nucleus. No
structure of plants and animals has received such detailed
and persistent investigation as has the nucleus, and much
of the advance in technique associated with the use of the
microscope has been stimulated by the necessity of learning
more about the nucleus.

If the nucleus is the conspicuous structure associated
with cell division, the suggestion is natural that it is the
material structure associated with heredity. But the
nucleus is a complex, and most conspicuous in its structure
is a substance called chromatin. In the ordinary nucleus
it appears as a network of denser material, which has
received its name from the fact that it takes stains easily,
being the most stainable substance in the nucleus (Fig.
2,a). If there is any definite material that deserves to be
called the physical basis of heredity, it is probably chro-
matin, which of course is a protoplasmic substance. This
belief is largely based upon the behavior of chromatin
during cell division.

In preparation for division, the chromatin network
becomes an evident continuous band, which resembles a
tangled skein (Fig. 2, 6). This band shortens and corre-
spondingly thickens, and finally breaks up into a definite
number of units, called chromosomes (Fig. 2, c). These
chromosomes are thus chromatin individually organized,

Physical Basis of Heredity and Evolution 27

in the same sense that protoplasts are protoplasm indi-
vidually organized, and they are thought to retain their
individual identity through all the apparent fusions into
bands and network. It is the chromosome, therefore,
consisting of the material chromatin, that is regarded as the
organized carrier of transmissible characters; hence the
behavior of the chromosomes in cell division becomes a

Fic. 2.—Diagram of stages in nuclear division.—After Lock

matter of first importance in considering the machinery of
heredity.

One of the important facts to note is the definite number
of chromosomes. Each kind of plant and animal has its
own number. For example, in certain plants the number
is 6; in others it may be considerably more than too; and
of course the intermediate numbers are well represented.
Differences in the number of chromosomes may occur

28 Heredity and Eugenics

among very closely related plants, or the number may be
constant throughout a great group. [or example, in the
gymnosperms, so far as known, the number is almost con-
stantly 12. This fact has given rise to the suggestion that
the number of chromosomes, as well as their quality, may
be a factor in heredity, but too much stress must not be laid
upon it as yet.

While the chromosomes are becoming separate, a spindle
of fibers is formed about the nucleus, and the chromosomes
become attached to the fibers, finally being arranged about
the equator of the spindle (Fig. 2, d). In this position,
each chromosome splits longitudinally (Fig. 2, e), and the
two halves, by the shortening of attached fibers, are drawn
toward the opposite poles of the spindle (Fig. 2, f), the
old chromosome thus being represented at each pole by a
half-chromosome. The half-chromosomes at each pole
enter into the organization of a new nucleus (I'ig. 2, g),
wall material is deposited in the plane of the equator of the
spindle and, extending through the cytoplasm, cuts the old
cell into two new cells, each with its nucleus (Fig. 2, i).
It is evident that each new nucleus has the same number
of chromosomes as the old one, and that each chromosome
of the new nuclei represents in material a chromosome of
the parent nucleus.

This detailed and precise process in the behavior of
chromosomes, insuring the transmission from one cell to
its progeny cells of the identical material contained in
every chromosome, is a strong argument in favor of regard-
ing the chromosome as the carrier of hereditary qualities.

The kind of reproduction with which the problems of
heredity are concerned chiefly, however, is that which
involves the fusion of sexual cells. There are three distinct

Physical Basis of Heredity and Evolution 20

methods of reproduction recognized among plants. The
most primitive method is vegetative multiplication, ordinary
vegetative cells producing new plants. In the transmission
of hereditary qualities this involves
simply a series of such cell divisions
as has been described above.

Later in the evolution of plants,
the power of reproduction was dis-
played chiefly by spores, which at
first were only certain protoplasts
that escaped from the incasing wall.
In most cases, before escape the
protoplast divides, so that there
issue from the old cell two or more
naked protoplasts or spores. Since
the early spores belonged to water
plants, they had swimming append-
ages (cilia), and were called swim-
ming spores or zodspores (Fig. 3, a
and 6). Any one of these swim-

zy , Tic. 3.—A portion of a fila-
ming spores, under appropriate ment of agreen alga (Ulothrix):

conditions, can produce a new in- 4; 200spores in mother cell; 6,

ss ° : an escaped zodspore; c, ga-
dividual. This method of multi- | ites most of which have

plying individuals remains the most — escaped from the mother cell;
effective method among plants. - re pening and Tusings
Vegetable multiplication and 77" ~
reproduction by spores are both sexless methods, and it is
quite evident that the introduction of the sexual method is
more significant than merely a third method of reproduction.
It is demonstrable among plants that the sexual cells
(gametes) were derived from the swimming spores (zodspores).
In certain plants, if a protoplast divides and gives rise to

20 Heredity and Eugenics

few and comparatively large protoplasts, they are swim-
ming spores (Fig. 3, a@ and 0), and each can reproduce. I
the divisions continue, however, and result in numerous
and comparatively small protoplasts, they are unable to
reproduce (Fig. 3, c). However, if they come together in
pairs and fuse (Fig. 3, d), thus making one cell (protoplast)
out of two (Fig. 3, e), the new cell can reproduce. This
fusion is the sexual act, and the fusing cells are the sexual
cells (gametes). It is of interest to note that this first
appearance of sex is quite disconnected with the multipii-
cation of individuals. Individuals are multiplied through-
out the growing season by the spores. Toward the close
of the season, the gametes begin to appear, and the fusion
cells (sygotes) formed by their pairing develop heavy walls
that protect them through the unfavorable season (as the
winter). All the other structures of the plant perish, and
it exists through the winter only in the form of zygotes.
At the beginning of the next season, the zygotes produce
new plants, and these are multiplied by spores. The
service rendered by the sex act in this case, therefore, is to
produce a protected cell, which can carry the plant through
an unfavorable period; in short, the service is protection
rather than multiplication.

The next advance in the evolution of sex was its differ-
entiation. The gametes at first are similar in appearance
and in behavior, but it must be recognized that this optical
test would be unable to detect any differences in quality.
It is upon the basis of appearance that such gametes are
said to be unisexual, which only means that they cannot
be distinguished as male and female. A series can be
arranged to illustrate a gradual differentiation of gametes
into two forms, unlike in appearance and in behavior. In

Physical Basis of Heredity and Evolution 31

one case, the gamete becomes larger and larger, its power
of movement diminishing at the same time, until at last
it becomes a very large and entirely passive cell. In the
other case, the gamete retains its small size and activity.
These two very dissimilar gametes are the egg and the
sperm, easily distinguishable female and male cells (Fig. 4).
The essential difference thus brought about is the great in-

Fic. 4.—A single large egg and numerous small sperms of rockweed (Fucus)

crease in the bulk of the gamete that becomes the egg,
but the constant feature, which is not changed, is the chro-
matin, the increase in bulk being due to an increase of
cytoplasm. This constancy of the chromatin, coupled with
the known fact that the two gametes contribute alike to
their progeny, indicates that the chromatin is the essential
material in heredity. Since both cytoplasm and nuclei are
involved in the sexual fusion, it may be claimed that the

iS}

Heredity and Eugenics

Ww

cytoplasm is as essential to the process as the nucleus; but
in certain plants, notably Lilium, it has been demonstrated
that when fusion occurs there is no cytoplasm whatsoever
investing the male nucleus. It seems safe to conclude,
therefore, that the nucleus contains the material essential
to the phenomena of heredity; and if so, chromatin
must be the material, and the chromosomes its visible
organized units.

A very simple case will serve to illustrate the results of
the sexual fusion upon the chromosome situation. Imagine

the fusion of an egg and a
4 sperm, each of whose nuclei

contains two chromosomes

(+) LB s (Fig. §,z and 2), ‘The nu-
1 ae cleus of the fertilized egg
: NO g would contain four chromo-

somes (Fig. 5, 3), two of
: oe te them maternal (contributed
- by the egg), and two of

Fic. 5.—Diagram illustrating result them paternal (contributed
of sexual fusion: zr, sperm containing two

chromosomes (4A); 2, egg containing by the sperm). Suppose
two chromosomes (BB); 3, fertilized egg that two of the four domi-
containing four chromosomes (two Pa- nate in determining the
ternal and two maternal); 4, domination een
of paternal chromosomes; 5 and 6,domi- structure of the new indi-
nation of one paternal and one maternal vidual to be developed from
chromosome; 7, domination of maternal per -
Sane arias the fertilized egg. It will
be seen that there are four
possible pairs: (1) the paternal pair (Fig. 5, 4), in which
case the new individuals would resemble the male parent;
(2) the maternal pair (Fig. 5, 7), in which case the resem-
blance would be to the female parent; (3) two pairs (Fig. 5, 5

and 6), each consisting of a dominant male and a dominant

Physical Basis of Heredity and Evolution 3

WwW

female chromosome, in which case the new individual would
be a mixture, resembling both parents. Expressing the
chances in the form of a ratio, they could be represented as
1:2:1. This is a simple expression of Mendel’s law, defined
in the preceding chapter. The formulation of Mendel’s
law was based upon the observed facts of heredity; and this
chromosome situation supplies for it a cytological basis.

It must be understood clearly that so simple an illus-
tration does not represent the actual facts, for chromosomes
are usually more numerous, and eggs and sperms already
contain a mixture of paternal and maternal chromosomes
derived from the preceding generations. It does illustrate,
however, the mixture of hereditary qualities by the sexual
fusion, the domination of certain of these qualities, and the
chances of resemblances in the progeny. It should be
understood also that the structural resemblance to the
maternal form or to the paternal form does not include sex
determination. For example, the new individual which
resembles the maternal form may prove to be either male
or female, and vice versa.

It is evidently impossible that the chromosomes con-
tinue to be doubled at each generation, without any reverse
process of reduction. The two cardinal points in every life-
history, therefore, are fertilization, by means of which the
chromosomes are doubled, and reduction, by means of
which the doubled number is halved. The reduction pro-
cess occurs at different stages in the life-history in different
organisms. Among animals, it occurs in connection with
the formation of the eggs and sperms; and therefore reduc-
tion and fertilization are practically consecutive events.
In most plants, however, the two processes are farther
apart, separated from one another by two distinct indi-

34 Heredity and Eugenics

viduals, one characterized by the reduced number of chro-
mosomes and bearing the sex organs (hence called the
gametophyte), the other characterized by the doubled num-
ber of chromosomes and producing spores (hence called
the sporophyte). In general, it may be said that among
animals reduction occurs in connection with gamete forma-
tion, while among plants it occurs
in connection with spore formation.

To use the simpler illustration
of animals, it is evident that the
cells making up the body of an
individual contain the doubled
number of chromosomes (Fig. 6,
1), derived from the fertilized egg
from which the body developed.
_ Fic. 6.—Diagram illustrat- When the sexual cells (eggs or
ing result of reduction: 1, ‘ ‘ wk
ordinary céllof the body cone SPeTms) of this imdividual are
taining doubled number of formed, the reduction occurs, and
“onions 2-3, the eggs or sperms contain the re
number, and illustrating the ducednumber. How the maternal
possibilities in the distribu- and paternal chromosomes are dis-
tion of paternal (4A) and A : : ri
iutishual (BBY clitemoceiies tributed in this reduction may not

be clear, but it is evident that

either eggs or sperms may contain chromosomes derived
from either line of descent (Fig. 6). In other words, it is
not inconceivable to think of an egg containing only chro-
mosomes derived from the paternal side, or of a sperm con-
taining only chromosomes derived from the maternal side,
or most likely of both eggs and sperms containing chromo-
somes derived from both sides (Fig. 6, 2-5).

These considerations indicate how every sexual fusion
results in a complex of possibilities, and the study of heredity

Physical Basis of Heredity and Evolution 35

is to discover whether these possibilities can be formulated
into a law.

In this connection, the phenomenon of parthenogenesis
should be referred to. By definition, it means the pro-
duction of a new individual by an unfertilized egg, and it is
a very common phenomenon among plants. When it is
remembered that ordinary cells can produce new individ-
uals by vegetative multiplication, and that spores can
reproduce, it should not be thought strange that so well-
nourished a cell as the egg can do the same thing. Among
the higher plants, however, in which the whole mechanism
has been worked out in greater detail, there is a significant
fact connected with the cases of parthenogenesis. In every
case investigated, the reduction in connection with spore
formation has not occurred, and therefore the unfertilized egg
contains the doubled number of chromosomes, just as though
it had been fertilized. In parthenogenesis, therefore, the
indications are that the fact to be explained is not reproduc-
tion by an unfertilized egg, but the failure of reduction.

The whole history of sexual reproduction among plants
indicates that its primary significance is not reproduction,
for probably many more individuals are produced by vege-
tative multiplication and by spores than by the sex act.
This would mean that the sexual method is chiefly con-
cerned with other results, which are secured in connection
with reproduction. These results seem to be the continual
securing of new combinations, and new combinations cer-
tainly make for evolutionary progress.

WILLIAM ERNEST CASTLE

Professor of Zodlogy, Harvard University

CHAPTER III
THE METHOD OF EVOLUTION"

No one today doubts the reality of evolution, at least
no one does who has had practical experience in animal or
plant breeding, and who has seen new forms of life come
into being under his own observation and guidance. But
the method of evolution is still in doubt. It is known in
general, that like begets like, but that occasionally it begets
unlike, and this may become a new race. As to how the
new race is begotten we have not got much beyond Darwin;
indeed many of us have not got so far. For Darwin recog-
nized two distinct ways in which new races may arise, but
many biologists today insist that there is only one way,
the way in which Minerva was begotten, who ‘sprang
full-fledged from the head of Jove.”” The modern name
for this method of origin is mutation, and its advocates,
like the ‘‘followers of the prophet,” insist that there is no
other.

Darwin was well aware that new races may arise in this
way, particularly under domestication, as in the case of
the Ancon ram and Niata cattle; but he believed that a
far commoner and more important method, particularly
among wild species, consists in a slow and gradual modi-
fication of the race, constantly in one direction, as under
the ever-growing power of a hydraulic press, until the

‘In these two chapters, especially in the second (chap. iv), material has been
drawn freely from the writer’s book on Heredity in Relation to Evolution and Animal
Breeding (D. Appleton & Co., New York), for which he has the kind permission
of the publishers. He also wishes to acknowledge aid given by the Carnegie
Institution to the investigations herein described.

39

40 Heredity and Eugenics

descendants become so different from their progenitors
that man assigns them to distinct races.

Now I am inclined to think that Darwin was on the
whole nearer the truth than the mutationists. They have
perceived a half-truth and perceived it more clearly than
did Darwin, but in scrutinizing this they have lost sight of
the larger picture which he saw. Darwin saw that new
races arise in two ways, and I shall attempt to show that
he was right.

First let us discuss the Minerva-like method of evolu-
tion, the birth of new races in a day, a method of great
theoretical interest and practical importance. What is
known about this method of evolution is commonly called
Mendelism, after Gregor Mendel, an Austrian monk of the
last century. Mendel was a school teacher who studied
as well as taught, and fortunately for us he studied from
the book of nature more than from other books. He
thought clearly about the things he saw, but wrote little.
Indeed we wish that he had written more, but perhaps if
he had done so he would have thought less well. Like most
profound thinkers, he was in advance of his day, so that
when he spoke, the “wise men”’ of the time failed to under-
stand him. The ‘wise man” to whom Mendel hoped to
make his ideas plain was the great German botanist, Karl
Naegeli, to whom Mendel wrote a number of letters about
his studies of plant hybrids. Naegeli failed to grasp the
important point in Mendel’s work, and the letters were for-
gotten until Mendel’s fame had become world-wide. Then
they were hunted up and published. Naegeli’s failure
to understand Mendel is after all not surprising; Mendel’s
thinking was in advance of his time. Several biological
principles now considered commonplaces were then un-

The Method of Evolution 41

known. When these had been established, Mendel’s law was
independently rediscovered long after his death. All honor
to the rediscoverers, DeVries, Correns, and Tschermak,
that, honoring the all-but-forgotten monk, they called the
new-found law Mendel’s, rather than their own!

In Mendel’s time little was known about the nature of
the reproductive bodies from which new individuals arise,
or of how these bodies are produced, or how they differ
from the organisms which produce them. These points
must be considered briefly.

An old but ever-recurring question in regard to heredity
is this: Does one generation inherit any part of the
experience of the previous generation ? In other words, is a
character acquired by one generation inherited by the next ?
This question, first raised in concrete form by Weismann,
has been discussed pro and con for many years, but the con-
sensus of scientific opinion at the present time favors Weis-
mann’s idea that acquired characters are not inherited.
In forming a judgment on this question, one fundamental
fact should be borne in mind, that in the higher animals
body plasm and germ plasm are distinct; that is, the body
is distinct from the reproductive cells which it contains, and
out of which the next generation is produced. Influences
which affect the body have no necessary influence on the
germ cells.

Weismann some years ago demonstrated this experi-
mentally for mutilations of the body. When the tails of
mice were cut off generation after generation, it was found
that young of the mutilated parents had tails as long as other
mice. More distinct evidence of the independence of germ
plasm and body is furnished by an experiment recently
performed by Dr. Phillips and myself.

42 Heredity and Eugenics

A young female albino guinea-pig approaching sexual
maturity was deprived of her ovaries, and into her body
was introduced the living ovary of a freshly killed black
guinea-pig, about three weeks old (Figs. 7 and 8). She
was later mated with an albino guinea-pig (Fig. 9).
By him she bore two litters of living young, and died
pregnant a little over one year after the operation, con-
taining a third litter (Figs. to-15). Had she not been
operated upon, her young by this male would undoubtedly
have been albinos, for albino guinea-pigs produce only
albino young, as several investigators have clearly shown.
But those young which she did bear were without exception
black, which character clearly they owed to the fact that
they developed from eggs produced by the ovary taken at
a very immature stage from a black animal. From evi-
dence such as this it is concluded that the inheritance can
not be affected by modifications of the body of the parent,
not even when the body is completely changed, since the
body, so far as heredity is concerned, is merely a container
of the reproductive cells. Yo modify the inheritance we must
modify the reproductive cells.

But the reproductive cells are not simple; they are
really dual in character, made up of equivalent parts
derived from father and mother. On this matter breeding
experiments throw light.

If a black guinea-pig of pure race is mated with an
albino, the offspring are all black, yet contain albinism as
a latent or recessive character. For if one of these black
offspring is now mated with the same albino, only half of
the offspring are black, the others being albinos. And if
two of the cross-bred blacks are mated with each other,
one-fourth of the young, on the average, are albinos, three-

Fic. 7.—A young, black guinea-pig, about three weeks old. Ovaries taken
from an animal like this were transplanted into the albino shown immediately
below it.

Fic. 8.—An albino female guinea-pig. Its ovaries were removed and in
their place were introduced ovaries from a black guinea-pig, like the one shown
in Fig. 7.

Fic. 9.—An albino male guinea-pig, with which was mated the albino shown
in Fig. 8.

Fics. 10-15.—Pictures of three living guinea-pigs (10-12) and of the pre-
served skins of three others (13-15), all of which were produced by the pair of
albinos shown in Figs. 8 and o.

The Method of Evolution 45

fourths being black (Figs. 16-19). This result is explained
in the following way. The cross-bred black individual
received from its black parent the character black (B),
and from its white parent the character white (W). In it
accordingly black and white were associated together, but
only the former was manifested, the white remaining hidden
by the black. But in reproduction the cross-bred black
individual transmits black and white in separate cells.
And since these two kinds of cells are in the long run equally
numerous, it follows that the cross-bred black individuals
produce both black and white offspring in proportions fairly
constant (Fig. 20).

Inheritance of this sort is called Mendelian, after Gregor
Mendel who first observed and explained it. The law
governing such inheritance is called Mendel’s law. Such
inheritance is satisfactorily accounted for by the assump-
tion that the reproductive cells are at first dual in nature,
but become simple before they can function in the pro-
duction of a new individual. For this assumption we have
abundant evidence furnished by the direct study of the
reproductive cells with the microscope. These cells, like
the cells of the body in which they are contained, show in
their nuclei at cell division a fairly constant number of
bodies known as chromosomes. In the worm Ascaris there
are only 2 of these chromosomes; in the sea-urchin Toxo-
pneustes there are 36; in mice and men, about 24.

A new individual arises, in sexually produced animals,
out of the union of an egg with a sperm. The sperm is
relatively small, but its influence equals that of the much
larger egg, which fact throws light on the nature of the
material basis of heredity. It suggests, namely, that
this material consists largely of ferment-like bodies which

Heredity and Eugenics

46

‘QI “SI Ul UMOYs sjeurue

aya Aq paonpoid SunoA inoy yo dnoiz y—'61 ‘ory “LI put gr ‘s3Iq orvdwog =*31d-eaums ourqe uv jo
: “QI ‘SI Ul WMOYs 9804} OFT] SuNcA ~— uv _ YOrTq & Jo Bunod dn-umoi3 oy} JO OMY—'SI “Ol
yoryq Jo ray yey ‘sid-eoums oem ourqye Uy—' LI ‘oly ‘Sunod Joy pue ‘sid-vaums o[emay HOeIq Y—9I ‘oly

The Method of Evolution 47

initiate specific metabolic processes in a suitable medium
represented by the larger portion of the egg.

In egg and sperm, before their union, the chromosome
number is reduced one-half, from the double to the single
condition; in Ascaris, from 2 to 1; in the sea-urchin, from
36 to 18; in the mouse and in the man from 24 to 12.
These reductions occur in what is called the maturation
of the sexual products.

In the male, the primitive germ cell containing the
double or 2V number of

chromosomes divides up (+) ()

into a group of four cells, Se

a te ° (*|*) ‘aveord
each containing the single or :
N number of chromosomes. fe See

ce e
This comes about by a fail- ea Jono aawcres

ure of the chromosomes to ay

: ea
split at one of the two cell oS ae
divisions which produce the ;
group of four sperm cells,
as they regularly do in Fic. 20.—Diagram to explain the result

° a veise shown in Figs. 16-19.
ordinary cell division. A
tadpole-like sperm now arises from each of the cells con-
taining the reduced number of chromosomes.

In the maturation of the egg, reduction is likewise
accomplished by two cell divisions, in one of which the
chromosomes do not split as in ordinary cell divisions.
The divisions of the egg, however, are into parts of very
unequal size, only one of which is fertilized, the rest failing
to develop. For example, in the marine worm Nereis,
according to Wilson, the maturation of the egg occurs
simultaneously with its fertilization. The first maturation
division separates off a minute cell, known as the first polar

ZYGOTES

2
2
S
S

48 Heredity and Eugenics

body, and is quickly followed by a second likewise unequal
division, by which a second polar body is produced. The
number of chromosomes remaining in the egg nucleus is
now reduced to half that in the egg before maturation. A
sperm entering the egg has formed within it a second nuclear
body which, like that of the egg contains a reduced number
of chromosomes. By the union of these two nuclei a new
nucleus is formed which contains the double number, and
from this all cells of the new individual are directly derived.
In all such cells the double chromosome number is present.
Similar events take place in the maturation and fertilization
of animal eggs in general.

Now, when the egg of a black guinea-pig is fertilized with
the sperm of a white one, or vice versa, protoplasmic con-
stituents unite which in one case are able to produce a
black coat, in the other a white one. These constituents,
whatever they are, evidently separate from each other and
pass into different cell products when the germ cells of the
cross-bred individual ripen. It seems natural to suppose
that the separation occurs at the reduction of the chromo-
somes from the double to the single condition. Half the
sperms, accordingly, of the cross-bred black individual bear
black, half white, none both; and the same is true of the
eggs (Fig. 20). Experiment proves conclusively that this is
so. Blackness and whiteness behave in crosses like indi-
visible units. They may be brought together repeatedly
in crosses, but always separate again at the maturation of
the gametes. We call them wnzt-characters. Black is a
positive unit (presence of black pigment), white its corre-
sponding negative (absence of black pigment).

Other unit-characters are quite independent, in their
inheritance, of black and white. Thus, the coat of a

did-voum3 ojyar ‘Ysnor W—'ts “Oly
sid-voumn3 yep ‘yJoowWs W—'1z “ol

Sid-vaumns yep ‘ysnor1 y—'bz ‘oly
sid-voumn3 oyYM ‘YJOous Y—'ez “OL

49

The Method of Evolution

‘uolajas Aq pasvaioul A]}eeI3 UsEq Sey

BULIATIS YJ, “SoUO Yep YUM possodssaqul sey oq
surejuod yeoo ayy, “std-vaumS pasaayis y—'gz “Oly S1d-voutn3 pajzjods ‘yqjoows ‘pomey-Bu0] W—"Lz “oly
sid-eoumns ayy ‘Ysnoi ‘pasey-Buojy y—"9z ‘OL Sid-voums oyYA ‘yOouIs ‘pomrey-Buo] W—"Sz “Oly

sairee
8
So
Q
3
5
2
S
ad
S
ny

92

The Method of Evolution 51

guinea-pig may be either rough or smooth (Figs. 21-24).
Rough is a unit-character dominant over smooth in crosses,
and among the second generation offspring from such a cross
occur three rough individuals to one smooth one. If the
rough parent is white (Fig. 23) and the smooth one dark
(Fig. 21), the parents differ in two unit-characters, and the
sequel shows that these are independent units. For
although the immediate offspring are all dark and rough
(Fig. 24), the next generation contains four sorts of indi-
viduals, representing all possible combinations of the two
alternative pairs of units: (1) smooth dark, like one grand-
parent (Fig. 21); (2) rough white, like the other (Fig. 23);
(3) rough dark, like the parents (Fig. 24); and (4) smooth
white, a new combination (Fig. 22).

Again, length of the hair is independent of its color or
roughness (Figs. 25-27). A short-haired colored animal
mated with a long-haired white one produces only short-
haired colored offspring, which, bred inter se, produce in
the next generation young of four sorts: (1) long white,
(2) short dark, (3) long dark, and (4) short white.

Recombinations in such ways can be accounted for if
we suppose each different unit-character to have its basis
in a different material body within the cell, perhaps in a
different chromosome or part chromosome. Thus, suppose
hair length to have its basis in one cell structure, which we
may represent in a diagram (Fig. 29) by a circle, and sup-
pose hair color to have its basis in another cell structure
represented by a square, and suppose further that these
two structures are independent of each other in their fusions
and segregations; then if we cross a long-haired white (LW)
animal with a short-haired dark one (SD), a combina-
tion (or zygote) will be formed showing only the dominant

52 Heredity and Eugenics

characters, short and dark hair, but able to transmit the
alternative conditions, long and white hair. At repro-
duction by such an individual, LZ will separate from S, and
W will separate from D, passing into a different cell prod-
uct, but it will be a matter of chance whether L is asso-
ciated with JW as originally, or with D. Hence the chances
are even for the production of the four kinds of gametes
shown in the diagram, LW, SD, LD, and SW, the visible
expression of which would

oe produce individuals in
character, respectively long

— a white, short dark, long dark,

apc and short white, as actually

obtained by experiment.
K 2 If the individuals crossed
are pure and differ in three
EXeCHCHCA omeve particulars, color, length,
Fic. 29.—Diagram to show the result and roughness of the coat,
of crossing a long-haired, white guinea- then their grandchildren
pig (L W) with a short-haired, dark one w]] be of eight sorts, repre-
ean senting all possible combi-
nations of three independent unit-character pairs, each of
which has its basis in a different material body in the cell.
A great many of the characters of animals and plants
behave as simple units in heredity, yielding a 3:1 ratio of
dominant to recessive individuals in the second genera-
tion from the cross. I have shown that this is true of
certain hair characters in guinea-pigs, namely, blackness,
roughness, and length of the hair. We have no idea how
numerous such characters are until they happen to be lost

in one individual or another. Then a new variation, a
sport or mutation, is observed. It is by this means, acci-

The Method of Evolution 53

dental loss of simple unit-characters, that the great color
variation of domesticated animals has arisen.

We should naturally consider the color character of a
wild mouse, rat, or rabbit, to be very simple, for we observe
such animals to breed very true to color, but the behavior
of the wild type in crosses shows it in reality to be very com-
plex, and to be the result of the simultaneous presence
of some half-dozen or more wholly independent unit-
characters. New color varieties have arisen by loss or modifi-
cation of one or more of these unit-characters. For example,
the wild house mouse by simple loss of three independent
factors has given rise to seven additional varieties known
among fancy mice.

The gray fur contains black, brown, and yellow pig-
ments disposed in a definite pattern in the individual hairs.
Loss of this pattern alone produces the black variety. Loss
of black produces the cinnamon variety; loss of both pro-
duces the brown or chocolate variety. Loss of the power
to produce color, that is loss of some general color factor,
produces an albino, whose breeding capacity will vary with
the number of other factors which it retains. Several other
color factors occur in mice, the loss of which has produced
new series of color varieties, but these will suffice to show
the process by which new varieties arise through loss of
unit-characters.

Simple unit-characters are not confined to the super-
ficial parts of an animal, as for example to its fur. We
know these superficial characters best probably simply
because they are most easily observed.

Loss of horns in cattle behaves as a dominant unit-
character; likewise in man a shortened condition of the
skeleton producing two-jointed instead of three-jointed

54 Heredity and Eugenics

fingers behaves as a simple dominant unit-character. A
curious affection of the nervous system producing the
waltzing condition of Japanese mice, behaves as a recessive
unit-character in crosses with the normal condition.

Is all inheritance unit-character inheritance? This
question cannot at present be answered fully, but many
facts indicate that it is. A large class of seemingly uncon-
formable cases which presented the greatest obstacle to such
a view has recently been brought into line with the unit-
character hypothesis. I refer to cases of blending inherit-
ance, in which the offspring are intermediate between the
parents, and this intermediate condition persists into the
next generation.

Size and skeletal proportions are inherited apparently
in this fashion. It is possible, however, that even in such
cases unit-character segregations may really occur, though
their presence is obscured because dominance does not occur.
For in plants such size segregations have been observed
recently by my colleague Dr. East and by others.

A single illustration will suffice. When varieties of maize
(or Indian corn) are crossed which differ in size of ear,
the hybrid plants bear ears of intermediate size but not
more variable than the more variable parent. The second
generation offspring, however, are extremely variable,
ranging in size from that of the smaller parent variety to
that of the larger.

The peculiarity of what we have called blending
inheritance lies partly in the entire absence of dominance.
In blending inheritance a unit-character represented once
in the fertilized egg has only half as much effect as one rep-
resented twice. In color inheritance, usually, but not always,
a single dose of a unit-character is as effective as a double

The Method of Evolution 55

dose in causing the development of the character. In size
inheritance, however, the single and double doses probably
produce very different effects.

A further apparent difficulty encountered in interpreting
blending inheritance as unit-character inheritance lies in
the multiplicity of the units involved, so that segregations
do not occur into a few discontinuous size classes, but into
classes so numerous and differing so little from each other
that it is very difficult to distinguish them.

Suppose that in crosses of black with white guinea-pigs,
black were represented by fwo unit-characters B and B’,
instead of by one, residing perhaps in different chromosomes,
and that either one of these could by itself produce black
color, then a larger proportion than three-fourths of the
second generation offspring would be black, namely, {+}.
If, further, the presence of a larger number of factors for
black produced more black pigment in the fur than a smaller
number produced, then we should have gradations of black-
ness among the second generation offspring as follows:
Aes Soe:

Add a third factor for black in the supposed cross,
located perhaps in a third chromosome, and the pure whites
would be reduced to 1 to 64 of the second generation off-
spring, while the different gradations or intensities of black-
ness would become 6, 5, 4, 3, 2, 1,0. The occasional white
individual would now differ so little from the lightest black
one that the two might often be confused, and there would
seem to exist all intermediate stages between pure white
and pure black, without entire segregation into either. By
selecting for the lightest or the darkest condition within a
mixed race of such second generation offspring one would
obtain with each selection a larger proportion of extremely

56 Heredity and Eugenics

dark or extremely light individuals, until a pure race was
obtained. Further, if the black character should become
attached to additional material bodies in the cell (chromo-
somes or the like), so that it would be represented by addi-
tional units, then the occurrence of light-colored progeny
would become still rarer, and deeper intensities of black-
ness than before existed would now occur. Thus selection
would become a means for the modification of a character
really dependent upon the inheritance of unchanging units.
Now this is perhaps what occurs when one seeks to modify
size by selection.

There are strong reasons for believing that mendelizing
characters can be modified by selection, though this idea
is vigorously denied by many Mendelians, as for example
by Johannsen. In Johannsen’s view, selection can do
nothing but sort out variations already existing in a race.
I prefer to think with Darwin that selection can do more
than this, that it can heap up quantitative variations until
they reach a sum total otherwise unattainable, and that
it thus becomes creative. I will describe briefly certain
experiences of my own which support this idea.

In several cases I have observed characters at first feebly
manifested gradually improve under selection until they
became established racial traits. Thus in guinea-pigs, the
hind-foot commonly bears three toes (Fig. 30, A). But
several years ago I observed an individual which had an
imperfectly developed fourth toe, similar to that shown in
Fig. 30,C. From the descendants of this animal, obtained
by inbreeding and selection, was formed a race having
well-developed fourth toes (Fig. 30, B) on both hind
feet. The extra toe made its appearance poorly devel-
oped on the left foot only. About 6 per cent of the

The Method of Evolution 57

offspring of this animal by normal unrelated mothers were
polydactylous, but among his offspring were some with
better developed fourth toes than the father possessed.
Such individuals were selected throughout five successive
generations, at the end of which time a good four-toed race
had been established. It was found in general that those
animals which had best-developed fourth toes transmitted
the character most strongly in crosses with unrelated normal
animals. The percentage of polydactylous individuals
produced in such crosses varied all the way from o to 100

Blige

Fic. 30.—A, hind-feet of an ordinary guinea-pig; B, of a four-toed guinea-
pig; C, of an imperfectly four-toed guinea-pig.

A

per cent. By selection this percentage was increased, as
was also the degree of development of the fourth toe in
crosses.

Another character which made its appearance among
our guinea-pigs, at first feebly expressed, was a silvering of
the colored fur, due to interspersing of white hairs with the
colored ones (Fig. 28). The first individuals observed
to have this character bore white hairs on the under surface
of the body only. By inbreeding, a homozygous strain of
the silvered animals was soon obtained, one in which all the
offspring were silvered to a greater or less extent. Selection

8 Heredity and Eugenics

mn

was now directed toward two ends: (1) to secure animals
which were free from spots of red or white, a condition
which was present in the original stock; and (2) to secure
extensive and uniform silvering on a black background.
In both these objects good progress has been made. We
have animals which are silvered all over the body except
on a part of the head, and the percentage of such well-
silvered individuals is relatively high.

A more extensive selection experiment is one in which
Ihave been assisted by Dr. John C. Phillips (Figs. 3rand32).

Fic. 31.—Diagram showing variation in the color pattern of hooded rats.
Numerals indicate arbitrary grades used.

Selection in this case has been directed toward a modifica-
tion of the color pattern of hooded rats, a pattern which is
known to behave as a recessive Mendelian character in
crosses with either the self (totally pigmented) condition
or the so-called Irish (white bellied) condition found in
some other rats. The extreme range of variation among
our hooded rats at the outset of this experiment is indicated
by the grades —2 and +3 of Fig. 31. Selection was now
made of the extreme variates in either direction and these
were bred separately. Two series of animals were thus

The Method of Evolution 59

established: one of narrow-striped animals, minus series;
the other of wide striped, plus series. In each generation
the most extreme individuals were selected as parents; in
the narrow series, those with narrowest stripe; in the wide
series, those with widest stripe.

ese
ee ae
| oe ieriieert eee
+3 lier ST
A ee ee eel
|
+2 E —
+41
10)
={
r———
A’ f—— ag 3 = ee
~-}---[- +
-2 =
ws
Generation 1 2 3 4 5 6 7 8

Fic. 32.—Chart showing effects of selection in eight successive generations
upon the color pattern of hooded rats. A, A’, average condition of selected
parents; B, B’, of their offspring.

The result of the selection is shown graphically in Fig.
32 (compare Table I). The offspring in the narrow series
became with each generation narrower; those in the wide
series became with each generation wider, with a single
exception. In the second generation the wide stock was
enlarged by the addition of a new strain of animals. This
caused a temporary falling off in the average grade of the
young, the two series overlapping for that generation. No

60 Heredity and Eugenics

new stock was at any other time introduced in either series,
the two remaining distinct at all times except in the second
generation. It will be observed that a change in the aver-
age grade of the parents is attended by a corresponding
change in the average of the offspring, and likewise in the
range of variation in the offspring. The amount of varia-
bility of the offspring is not materially affected by the
selection, but the average about which variation occurs is
steadily changed, as are also the limits of the range of
variation.
TABLE |

RESULTS OF SELECTION FOR MODIFICATION OF THE COLOR-PATTERN OF
Hoopep Rats

Generation ae) Saat) Mee
Plus series 1..... eR ERGSE ESS | B56 2.05 150
Ba ibid ing Sin ae. e Se. esen 2.51 1.92 471
Spa eee ae oaa Rates 2.93 2-51 341
Ae eanduciead Sh Gna te 3.09 2.92 444
Shs Sviosekes ava esap seuaneanige eto 3-33 2.90 610
DU ESAES the Steet oer ee oes 3.00 834
Pe ee ee ee 3.83 2.14 874
a ee ee Oe ee ee 3.05 3.30 gt
MO Balls Svansetsh easrsh assed ueue actors. craileiersthedete stesinus elerats le, pea ea oa Ne 3,815
Mantis Seriesiits.ic Nate La ateetletier ae 1.46 1.00 55
BS iu Aventis te a ree 1.41 1.07 132
eer ie ee re 1.56 1.18 195
AER ASCE SO OS Co 1.69 1.28 320
Gaba ee wehammele see Lave 1.41 7OI
Ose ceca, eet pee AON Ser 1.86 1.56 1,252
DERE ITEE ede Ree aR aE 2.00 1.70 1,544
Oita ae orn ATG 2.03 r.78 pee
Ota scescieaceusta cg apacataneevdents wed Anil latinas abcnpesiatsaeiods | eer ct 4,921

The interesting feature of this experiment is the pro-
duction, as a result of selection, of wholly new grades, in
the narrow series of animals having less pigment than any
known type other than the albino; in the wide series, of

The Method of Evolution 61

animals so extensively pigmented that they would readily
pass for the “Irish type,’ which has white on the belly
only, but which is known to be in crosses a Mendelian alter-
native to the hooded type. By selection we have practi-
cally obliterated the gap which originally separated these
types, though selected animals still give regression toward
the respective types from which they came. But this
regression grows less with each successive selection and ulti-
mately should vanish, if the story told by these statistics
is to be trusted. As yet there is no indication that a limit
to the effects of selection has been reached.

From the evidence in hand we conclude that Darwin
was right in assigning great importance to selection in
evolution; that progress results not merely from sorting
our particular combinations of large and striking unit-
characters, but also from the selection of slight differences
in the potentiality of gametes representing the same unit-
character combinations.

Accordingly we conclude that unit-characters are not
unchangeable. They can be modified, and these modifica-
tions come about in more than a single way. Occasionally
a unit-character is lost altogether or profoundly modified
at a single step. This is mutation. But more frequent
and more important, probably, are slight, scarcely notice-
able modifications of unit-characters that afford a basis for
a slow alteration of the race by selection. Mutation, then,
is true, but it is a half-truth; selection is the other and
equally important half of the truth of evolution, as Darwin
saw it and as we see it.

CHAPTER IV
HEREDITY AND SEX?

The value of a domesticated animal often depends in
considerable measure on its sex. ‘Therefore, if a means
could be devised for controlling the sex of offspring, it
would be of great economic value to the breeder. Endless
attempts have been made to do this, and occasionally a
claim of success has been made, but none of these claims
has withstood the test of critical analysis or experiment.
The hypotheses advanced to explain how sex may be con-
trolled have been of the most varied character. In some
the determination of sex has been supposed to inhere in the
nature of the parents, in others it is referred to conditions
of the gametes themselves.

Relative age or vigor of the parents has been supposed
to influence sex in various ways. The same idea has been
advanced regarding the gametes themselves, it being
supposed that early or late fertilization of the egg might
influence its sex. Experimental evidence, however, as to
these several hypotheses is wholly negative, when one elimi-
nates other possible factors from the experiment. Every-
thing points to the conclusion that sex rests in the last

‘In reading this chapter, the following definitions should be kept in mind.

Gamete: a mature reproductive cell capable, on uniting with another gamete,
of forming a new individual.

Zygole: the new individual formed by the union of two gametes.

Homozygole: an individual formed by the union of two gametes of like char-
acter as regards heredity

ITeterozygote: an individual formed by the union of two gametes of unlike
character as regards heredity.

62

Heredity and Sex 03

analysis upon gametic differentiation, just as the color of a
guinea-pig in a mixed race of blacks and whites depends
upon whether the gametes which unite to produce it carry
black or white. As the heterozygous black guinea-pig
forms black-producing and white-producing gametes in
equal numbers, so there is reason to think male-producing
and female-producing gametes are formed in equal numbers
by the parent, in many cases at least. But is it not possible
that there may exist individuals which produce the two
sorts of gametes in unequal numbers, and so would have a
tendency to produce more offspring of one sex than of the
other? Perhaps so, though we have no evidence that such
a condition, if it does exist, is transmitted from one genera-
tion to another. On this point I made experimental
observations upon guinea-pigs, extending over a series of
years. Oftentimes I found an individual that produced
more offspring of one sex than of the other, but this was
probably due merely to chance deviations from equality.
I could get no evidence that the condition was inherited,
though the experiment was continued through as many
as seven generations, including several hundred offspring.

The essential difference between a female and a male
individual is that one produces eggs, the other sperm. All
other differences are secondary and dependent largely upon
the differences mentioned. If in the higher animals (birds
and mammals) the sex glands (i.e., the egg-producing and
sperm-producing tissues) are removed from the body, the
superficial differences between the sexes largely disappear.
In insects, however, the secondary sex-characters seem to
be for the most part uninfluenced by presence or absence
of the sex glands. Their differentiation occurs independ-
ently though simultaneously with that of the sex glands.

64 Heredity and Eugenics

The egg or larger gamete (the so-called macro-gamete)
in all animals is non-motile and contains a relatively large
amount of reserve food material for the maintenance of the
developing embryo. This reserve food material it is the
function of the mother to supply. In the case of some
animals, for example flatworms and mollusks, the food
supply of the embryo is not stored in the egg cell itself, but
in other cells associated with it, and which break down and
supply nourishment to the developing embryo derived from
the fertilized egg. Again, as in the mammals, the embryo
may derive its nourishment largely from the maternal
tissues, the embryo remaining like a parasite within the
maternal body during its growth, feeding by absorption.
But in all cases alike the mother supplies the larger gamete
and the food material necessary to carry the zygote through
its embryonic stages. The father, on the other hand,
furnishes the bare hereditary equipment of a gamete, with
the motor apparatus necessary to bring it into contact with
the egg cell, but without food for the developing embryo pro-
duced by fertilization. The gamete furnished by the father
is therefore the smaller gamete, the so-called micro-gamete.

From the standpoint of metabolism, the female is the
more advanced condition; the female performs the larger
function, doing all that the male does in furnishing the
material basis of heredity (a gamete), and in addition
supplying food for the embryo. As regards the reproduc-
tive function, the female is the equivalent of the male
organism, plus an additional function, that of supplying
the embryo with food. When we come to consider the
structural basis of sex, we find reasons for thinking that
here, too, the female individual is the equivalent of the
male plus an additional element. The conclusion has very

Heredity and Sex 65

naturally been drawn that if a means could be devised for
increasing the nourishment of the egg or embryo, its develop-
ment into a female should be thereby insured, while the
reverse treatment should lead to the production of a male.
But in practice this a-priori expectation is not fulfilled.
Better nourishment of the mother may lead to the produc-
tion of more eggs, but not of more female offspring, as ha¢
repeatedly been demonstrated by experiment. Also poor
nutrition of the mother may diminish the number of eggs
which she liberates, but will not increase the proportion
of males among the offspring produced.

An excellent summary of evidence on this point was
made by Cuénot in 1900. Attempts to influence the sex
of an embryo or larva by altered nutrition of the embryo
or larva itself have proved equally futile. Practically the
only experimental evidence of value in favor of this idea
has been derived from the study of insects, and this is
capable of explanation on quite different grounds from
those which first suggest themselves. It has sometimes been
observed, as by Mary Treat for example, that a lot of insects
poorly fed produce an excess of males. In such lots, how- 7
ever, the mortality is commonly high, and more females die
than males, because the female is usually larger and requires
more food to complete its development. The fallacy in
concluding from such evidence that scanty nutrition causes
individuals which would otherwise become females to
develop into males was indicated years ago by Riley.
Nevertheless an argument for the artificial control of sex
based on such evidence is from time to time brought forward,
as, for example, a few years since by Schenk. The lates.
advocate of sex control by artificial means is an Italian.
Russo (1909). He claims in the case of rabbits that by

66 Heredity and Eugenics

feeding the mother on lecithin or by injections of lecithin,
the proportion of female births may be increased. His
evidence in support of this claim is, however, wholly inade-
quate, and two independent repetitions of his experiments,
made by Basil in Italy and by Punnett in England, have
given entirely negative results.

An alternative hypothesis concerning the determination
of sex has been steadily gaining ground during the last ten
years, that sex has its beginning in gametic differentiation
and is finally determined beyond recall in the fertilized
egg by the nature of the uniting gametes. Instructive in
this connection is a study of parthenogenesis, reproduction
by unfertilized eggs. But before entering upon this, it
may be well to review briefly the changes which regularly
take place in the egg which is to be fertilized, and compare
with this the changes which occur in eggs not to be fertilized.

In each cell of the ordinary animal there occurs a charac-
teristic number of bodies called chromosomes. We do not
know that they are any more important than other cell
constituents, but we know their history better. These are
contained in the nucleus of the cell, and at the time of
nuclear division they are found at the equator of the division
spindle. There each of them regularly splits in two, and
one derivative goes to either end of the spindle, and so into
one of the daughter nuclei. Thus each new nucleus has,
as a rule, the same chromosome composition as the nucleus
from which it was derived.

But the egg which is to be fertilized undergoes two
nuclear divisions in succession, in only one of which do the
chromosomes split. In the other division the chromo-
somes separate into two groups without splitting, and each
group goes into a different cell product. Consequently,

Heredity and Sex 67

in each of these products the number of chromosomes is
reduced to half what it is in the cells of the parental body.
Thus in the egg of the mouse, by maturation, the number
of chromosomes becomes reduced from about twenty-four
to about twelve.

Similar changes occur in the developing sperm cell
(Fig. 33, upper row). Starting with the double or 2NV
chromosome number, there are formed by two nuclear
divisions, with only one splitting of chromosomes, four
cells, each with the reduced

or simplex number of chro- (@) q (x) Q® me ra

mosomes, V. From each of WW a

these four cells arises a
tadpole-like sperm. Con- O ee a)
sequently, when the sperm (nv) (w)(n)

enters the egg at fertiliza- ye zs
tion it brings in a group Fic. 33.—Top row, normal spermato-
of NV chromosomes (in the genesis; lower row, spermatogenesis of
mouse apparently 12), a a

which, added to the egg contribution of NV chromosomes,
brings the number in the new organism again up to 2N (in
the mouse 24).

Now, as regards the maturation of parthenogenetic eggs,
those which are to develop without having been fertilized,
three categories of cases deserve separate discussion. The
simplest of these in many respects is found among the
social hymenoptera (ants, bees, and wasps) (see Fig. 34,
left column). The eggs are, so far as we can discover, all
of a single type. They undergo maturation in the manner
already described, the chromosomes being reduced to the
N or simplex number. The eggs of most animals, after
they have undergone reduction, are incapable of develop-

68 Heredity and Eugenics

ment unless fertilized, but those of the hymenoptera may
develop either fertilized or unfertilized. In the former
case a female is produced, in the latter a male. The simplex

or V condition is in this case the male, the duplex or 2

BEE ROTIFFR APHID

(FAVORABLE f

Fic. 34.—Sex determination in par-
thenogenesis. Top row, nuclear condition
of the parthenogenetic mother; second
row, of her eggs when they develop with-
out nuclear reduction, having formed a
single polar cell; third row, condition of
the eggs after complete maturation—the
unfertilized egg in each case produces a
male; fourth row, nuclear condition of
the fertilized egg, always a female.

condition is the female,
naturally the one of higher
metabolic activity, the one
which forms the macro-
gametes.

There is a peculiarity in
the maturation of the sperm
cells of male animals of this
sort (Fig. 33, lower row).
The cells of the male are in
this case already in the re-
duced or simplex condition,
N. In the production of
the sperms the reducing
division is omitted so far as
nuclear components are
concerned, so that each
sperm formed contains the
full simplex chromosome
number, V. If it were less,
the gamete formed would

perhaps not be capable of transmitting all the hereditary
characteristics of an individual.

A second category of cases (Fig. 34, middle column)
is represented by such simple aquatic organisms as rotifers
and small crustacea, like Daphnia. In these partheno-
genesis occurs exclusively when the food supply is very
abundant and conditions are otherwise favorable, whereas

Heredity and Sex 69

reproduction by fertilized eggs occurs only when external
conditions, including food supply, are not good. Under
favorable conditions only female offspring are produced.
The conclusion has naturally but erroneously been drawn
that good nutrition in itself favors the production of females
in animals generally, which is not true. The egg produced
by Daphnia, or by a rotifer, under optimum conditions
does not undergo reduction (Fig. 34, second row). It remains
in the 2N condition, forming but a single polar cell. It is
therefore unprepared for fertilization, and in fact it is not
fertilized. Its sex is like that of the animal which formed
it, female. Under unfavorable conditions, however, the
eggs of the rotifer and of Daphnia do not begin development
until they have undergone maturation. They are also of
two sizes (Fig. 34, third row)—small eggs, which develop
without fertilization and which form males, and large eggs,
which require fertilization, and which form females. In
this category of cases, as in that of the hymenoptera, the
egg which develops in the 2 condition, either from failure
of reduction to occur in maturation or from fertilization
following reduction, forms a female; whereas the egg which
develops in the V condition forms a male.

In a third category of cases there is a quantitative
difference in chromatin between male and female, just as
in the foregoing cases, but this does not amount to a whole
set of chromosomes, V, but to only a partial set, one or
two chromosomes (Fig. 34, right column). This category
of cases occurs in plant lice (aphids and phylloxerans);
evidence of its existence rests chiefly on recent observations
made by von Baehr and Morgan. Females are formed by
parthenogenesis without reduction, occurring under favorable
conditions, just as in the case of rotifers. Females are also

70 Heredity and Eugenics

formed by fertilization following reduction under unfavor-
able conditions, just as in rotifers. In both cases the female
is2.V. Males arise only by parthenogenesis under unfavor-
able conditions, just as in rotifers, but the reduction which
occurs before development begins is partial only. A whole
set, NV, of chromosomes is not eliminated in maturation, but
only 1 or 2 chromosomes. Hence the male condition here
is 2V—1 or —2. The condi-
tion of the gametes formed,
however, is NV in both sexes.
In spermatogenesis, division
of the germ cells takes place
into VN and N—1 daughter
cells, but the latter degene-
rate (like the non-nucleated
cells of the bee and wasp),
and only the former produce
spermatozoa. Hence in ferti-
lization only 2N zygotes are
produced, which are invari-
ably female.

Summarizing the three

Fic. 35.—Diagram of sex determi- categories described, we may
nation when the female is homozygous,

say that in all known cases of
parthenogenesis, the female
is in the duplex (2) condition, the male in the simplex
(Ny o ) or partially duplex condition (2 —t, or 2N ==9)). ihe
female in all cases has the greater sr ONCE content.

In a great many insects and other arthropods, which
are not parthenogenetic, it is known that, although the
male, like the female, develops only from a. fertilized egg,
nevertheless the male possesses fewer chromosomes than

the male heterozygous.

———

Heredity and Sex vB

the female. In such cases the female forms, as in cases of
parthenogenesis, only N gametes, but the male forms
gametes of two sorts, N and N—1 or N—2 (Fig. cio
In consequence zygotes of two sorts result, those which are
2N, female, and those which are 2V—1 or 2V—2, male.
Thus in the squash bug, Anasa tristis, according to Wilson,
the mature egg contains rr chromosomes, the spermatozoa
either to or 11 chromosomes, the two sorts being equally
ee ee

numerous.
sa es

Egg r1-++sperm 11 produces a zygote 22 (2), a female

Egg 1r+sperm ro produces a zygote 21 (2N-1), a male
N in this species=11; 2NV=22, the female: 2N —1=21,
the male. Males and females are therefore approximately
equal in number, as in most animals where the two sexes
are not subject to unequal mortality. In the Mendelian
sense the female is in such cases a homozygote, the male a
heterozygote. The sex of an individual in such cases
depends upon which sort of a sperm chances to enter the
egg.

But the experimental evidence indicates that both as
regards sex and as regards heritable characters correlated
with sex, these relations may in some cases be reversed, the
female being heterozygous, the male homozygous. In such
cases there is reason to think that structurally the male is
2N but the female 2V+. That is, the female is still the
equivalent of the male plus some additional element and
function. A structural basis in the chromosomes for such a
condition has been described by Baltzer in the case of the
sea-urchin. He found the regular duplex number of chromo-
somes in the male; but in the female, while the number was |
the same, one of the chromosomes was larger than its mate, |
having an extra or odd element attached to it. In such a

42 Heredity and Eugenics

case the gametes formed by the male would all be NV, but
those formed by the female would be of two sorts equally
numerous, viz., V and V+ (Fig. 36). Egg WN fertilized by
sperm N would produce a zygote 2N, a male; egg N+
fertilized by sperm V would produce a zygote 2V+, a
female. Hence, here as in other animals, the sexes would
be approximately equal, but.
the sex of a particular indi-

vidual would depend upon
which sort of egg gave rise

©).
|
©),

—

g ~~ Upon the existence, as in

US ‘ N the foregoing cases, of an
a 4 | unpaired or odd_ structural

a V1 element in the egg, may per-

\ of a curious sort of heredity

) known as sex-limited heredity.

(@)? (@)8 Everyone who knows any-

thing about poultry is ac-

Fic. 36.—Diagram of sex determi- quainted with the popular

nation when the female is heterozy- American breed called barred
gous, the male homozygous.

Plymouth Rock. In this
breed the feathers are marked with alternate bars of darker
and lighter black. Pure barred Rocks breed true, but when
crossed with other breeds, the male proves to be homozy-
gous, the female heterozygous in barring. For the male
Rock crossed with a non-barred breed produces only barred
offspring in both sexes, but the female Rock crossed with
the same non-barred breed produces offspring approxi-
mately half of which are barred, the other half being

non-barred. Further, the barred individuals in_this cross

4 i haps depend the explanation

Heredity and Sex 73

are invariably males, the non-barred ones being females.
Accordingly, the distribution of barring and non-barring
in the cross is sex limited.

The barred offspring produced by a cross between
barred Plymauth Rocks and a non-barred breed, whether
those offspring are males or females, prove to be heterozy-
gous in barring, as we should expect, the- barring factor
having been received only from one parent, the barred one.
Further, the non-barred_offspring produced by a_barred
Rock female crossed with a non-barred breed, do not trans-
mit barring, hence they are pure recessives as regards ,
barring. Hence, also, we are forced to conclude, as alread
suggested, the female of the pure barred Rock breed
heterozygous as regards barring, and transmits the char.
only to her male offspring, her female offsprin
father is non-barred), neither being themselves b
“being able to transmit barring.

A pure ‘Plymouth Rock race breeds tru
merely because all its males are pure, for
not pure. This is shown by the folloyfng experiment.
If a heterozygous barred male, produce a cross between
a Rock and a non-barred breed, is#rossed with barred
females, either those of a pure Rockgface or those produced
by a cross, the result is the same#f¥ The male offspring are
all barred; the females, half them barred, half non-
barred. This result shows th -all’ barred females alike
are heterozygous in barring. |

Sex-limited inheritance such as this finds at the “nts|

o_barring
females are

time its most probable explanation in the existence in the
egg of an extra or plus element never found in the sperm,
this element pairing with the sex-limited character in the
reduction division. Thus, in the barred Rock, calling

74 Heredity and Eugenics

barring B, the male of pure race is plainly BB and every
sperm is B. But the female clearly contains only one B
and cannot be made to contain two. Perhaps a second B
is kept out by some structural element, XY, the distinctive
structural element of the female individual. Then the
eggs will be of two sorts: B and X (Fig. 37). Since the
sperms are all B, the first type of egg when fertilized will
FEMALE Mae contain BB, a homozy-
gous barred individual

and a male, since it
lacks Y; the second

type will contain BX,
a bird heterozygous in

B Bite barring, and a female,

/ since it contains X.

This agrees with the
experimental result.

A heterozygous

B\B barred male will form

Fic. 37.—Diagram of sex-limited inheritance two kinds of sperm,

when the female is a heterozygote, as in barred only one of which will

fowls. X, female sex determiner; B, barring. can Are :
contain B. If such a

male be mated with a barred female, four sorts of zygotes
should result as follows:

Gametes of heterozygous barred male=B and —

Gametes of barred female =BandX
Zygotes=B - B (homozygous barred male); B - — (heterozygous
barred male), B - X (barred female), and — - X (non-barred female).

The observed result of this cross accords fully with the
foregoing expectation.

The sex-limited inheritance of barring in fowls may
explained, as we have just seen, on the assumption that the

Heredity and Sex 75
female is the heterozygous sex. The same is true_of sex-

limited inheritance in canary birds and in the moth, Abraaas,
according to Bateson and Doncaster. But these relations are
exactly reversed in the pomace fly, Drosophila ampelophila
according to Morgan.

regards some cell structure, Y, which in the male is never
Ree ee ee eee
represented mor th FEMALE MaLe

once. Accordingly,

the formula of the RXR «rl )
female is in such cases ,

XX; that of the male,

X—. Now the sex- |

limited characters in C)
Drosophila seem to be

bound up with the Y

structure, not repelled \

by it, as is barring in
fowls. Accordingly, a XRXR XR
sex-limited character ae

Fic. 38.—Diagram of sex-limited inheritance
may be represen ted when the female is a homozygote, as in the red-

twice in the female eyed Drosophila. X, sex determiner; R, red
Drosophila, but only ce

once in the male; or in other words, the female may be
homozygous as regards a sex-limited character, but the
male can only be heterozygous (Fig. 38).

Drosophila normally has red eyes, but the redness of
the eye is a distinct unit-character, sex limited in heredity.
Further, males are regularly heterozygous in this character,
while females are homozygous. For Morgan has obtained
a race in which the eyes are white, owing to the loss of the
red character; and reciprocal crosses of this race with

76 Heredity and Eugenics

ordinary red-eyed animals yield different results. ‘The
red-eyed female crossed with a white-eyed male produces
@ white-eyed female produces offspring only half of which
are red eyed, viz., the females, whereas the males are

white eyed. —
These different results in the two cases apparently come
about as follows:

FIRST CASE

Gametes of red-eyed female =X-R and X-R
Gametes of white-eyed male =X and —
Zygotes=X - X-R (red-eyed female), and —-X-R (red-eyed male).

SECOND CASE

Gametes of white-eyed female =X and X
Gametes of red-eyed male =X-R and —
Zygotes=X - X-R (red-eyed female), and — - X (white-eyed male).

A short condition of the wings in Drosophila, which
renders the animal incapable of flight, is likewise sex
limited in heredity, as has been shown by Morgan. By
crossing two races of Drosophila, each of which possessed a
different sex-limited character, Morgan has been able to
combine the two characters in a single race. Thus was
obtained a race both white eyed and short winged. The
synthesis cannot be made originally in a male individual,
but only in a female. For only in the female can the two
characters be brought together, cach associated with a
different Y, since in the male only one Y is present. Al-
though each sex-limited character seems to be attached
to or bound up with an X structure, it evidently has a
material basis distinct from_y. Otherwise it would_not

Heredity and Sex 77

be possible for the character to leave one Y and attach
itself to the other, as apparently takes place in the female
when the combination of two sex-limited characters in the
same gamete is secured through a cross. The combination
is apparently secured in this way:

Gametes uniting, X¥-R and Y—L
Zygote formed, X-R - X-L
Its gametes, X-R and X-L, or X-R-L and X.

One of the uniting gametes, X-R, is formed by the
red-eyed, short-winged parent; the other, X-L, is formed
by the long-winged, white-eyed parent. The zygote result-
ing is a red-eyed individual, since it contains R; it is long
winged, since it contains LZ; it is a female, since it contains
two Xs. Now, its gametes are of four sorts, as indicated.
The first two sorts result from simple separation of the
two Xs, each with its associated character, R in one case,
L in the other. But the third sort could result only from
the attachment of R and LZ to the same X, leaving the other
X without either R or L as the fourth kind of gamete.
This kind, which transmits neither red eyes nor long wings,
would represent the new gametic combination—white eyed
and with short wings.

—The experimental evidence that gametes of these four
sorts are formed by females of the origin described is as
follows: When such a female is mated with a long-winged,
white-eyed male, there are obtained female offspring, all
of which are long winged, but half of them are red eyed,
half white eyed. The male offspring, however, are of four
sorts, viz., red short, white long, red long, and white short.
This result harmonizes with the hypothesis advanced.
For if the gametes of the female are X-R, X-L, X-R-L,

78 Heredity and Eugenics

and Y, and those of the male are X-L and —, then the
following combinations should result:

X-L-. X-R, red long female

X-L-X-L, white long female

X-L - X-R-L, red long female

X-L.X, white long female

— - X-R, red short male

——.-X-L, white long male

— -NX-R-L, red long male

—.V\, white short male

This expected result accords with that actually obtained
by Morgan.

Color-blindness in man is a sex-limited character, the
inheritance of which resembles that of white eyes or short
wings in Drosophila, rather than of barring in poultry.

Color-blindness is much commoner in men than in
women. A color-blind man, however, does not transmit
color-blindness to his sons, but only to his daughters, the
daughters, however, are themselves normal provided the
mother was; yet they transmit color-blindness to half
their sons. <A color-blind daughter could be produced,
apparently, only by the marriage of a color-blind man with
a woman who transmitted color-blindness, since the daugh-
ter to be color-blind must have received the character from
both parents, whereas the color-blind son receives the charac-
ter only from his mother.

Color-blindness is apparently due to a defect in the
germ cell—absence of something normally associated there
with an Y-structure, which is represented twice in woman,
once in man. Color-blindness follows, therefore, in trans-
mission, the scheme shown in Fig. 38.

Heredity and Sex 79

If, as has been suggested, the determination of sex in
general depends upon the inheritance of a Mendelian factor
differentiating the sexes, it is highly improbable that the
breeder will ever be able to control sex. Male and female
zygotes should forever continue to be produced in approxi-
mate equality, and consistent inequality of male and
female births could result only from greater mortality on
the part of one sort of zygote than of the other. Only in
parthenogenesis can man at will control sex, and until he
can produce artificial parthenogenesis in the higher animals,
he can scarcely hope to control sex in such animals.

Negative as are the results of our study of sex control,
they are perhaps not wholly without practical value. It is
something to know our limitations. We may thus save
time from useless attempts at controlling what is uncon-
trollable and devote it to more profitable employments.

EDWARD MURRAY EAST

Assistant Professor of Experimental Plant Morphology
Harvard University

CHAPTER V
INHERITANCE IN THE HIGHER PLANTS

The general acceptance of the theory of organic evolu-
tion made necessary a new botany as well as a new zodélogy.
The artificial classification of plants in general use a half-
century ago has been replaced by one based upon the natural
relationships that have linked together plant groups during
their progressive changes. The need of new facts in the
prosecution of this great work has played no small part in
the rise of plant morphology, histology, physiology, and
ecology to well-deserved places of eminence in science.
But in so far as the valuable subject-matter of these botani-
cal sciences have touched or been touched by conceptions
of evolution, they have, in general, simply contributed
additional facts which have harmonized with and supported
that great truth already so well established by Darwin.

Such a historical point of view did not fully satisfy the
seeker after knowledge. He wished to know why and how
these things came about. In the gratification of this
curiosity as to the mechanism of heredity, of evolution, and
of the changes that occur under domestication, rapid prog-
ress has recently been made. The botanist has joined hands
with the zodlogist and a new subdivision of the biological
sciences—Genetics—has arisen.

As subject-material for use in attacking genetic problems,
plants and animals each have advantages and disadvan-
tages; but the results of the botanist and of the zodlogist
kave been wonderfully harmonious. The same methods are
used by both, and the work of the pedigree culturist, the

83

34 Heredity and Eugenics

histologist, and the biological chemist supplement each
other in a way that bespeaks a most hopeful future. We
shall discuss some results obtained by the use of the oldest
method, that of the garden, or, to give it the more aristo-
cratic name, the pedigree culture.

This method is old, but its most important results are
modern. A century and a half ago Kolreuter carried out
the first systematic studies in plant hybridization. Through
them he was able to show that most reciprocal crosses are
identical, and therefore that the pollen grain is as essential
and important in determining the characters of a hybrid
as is the ovule. Koélreuter, of course, did not know the
true process of reproduction, but he came as near the truth
as could have been expected at the time by showing that
an application of 50 or 60 pollen grains was sufficient for
the production of over 30 seeds.

Kolreuter, and a little later Thomas Knight, both found
that hybrids were in general more vigorous than either of
the parents; and Knight from this fact argued rejuvenation
by hybridization and promulgated what afterward came to
be known as the Knight-Darwin law. This was stated by
Darwin in the aphorism, ‘Nature abhors perpetual self-
fertilization.”” Our views on this subject, as will be shown
in the next chapter, must now be considerably modified;
nevertheless Knight partially outlined a great truth.

One other plant breeder must be mentioned as markedly
in advance of his age. The elder Vilmorin in the middle of
the nineteenth century established a principle which has
not until recently been given,the credit it deserves. Vil-
morin insisted that the only method of improving plants
by selection is to judge each plant by the average condition
of its progeny. This is Vilmorin’s isolation principle and

Inheritance in the Higher Plants 85

is the direct ancestor of Johannsen’s genotype conception
of heredity.

Other items of fact and improvements upon technique
were numerous then as they are today, but these few dis-
coveries comprise the only notable contributions of the
hybridizers until Abbot Mendel’s epoch-making researches
on the pea (Piswm sativum) in the little cloister garden at
Brinn.

The elements of Mendelianism as they apply to animals
have already been discussed. In taking up some of the
important neo-Mendelian facts as they are found in the
higher plants, I propose to describe types of Mendelian
inheritance with the idea of showing how facts that are
apparently non-related may be included under one descrip-
tive notation. The illustrative material is drawn largely
from my own pedigree cultures of maize or Indian corn
because they are naturally more familiar, but the points
discussed by no means apply only to corn.

It is of no small importance that strict Mendelian nota-
tion has been found to apply to the facts of inheritance in
both plants and animals. Sex has arisen separately in both
kingdoms, and probably even more than once in the vege-
table kingdom. It is therefore a great argument for the
universality of Mendelian inheritance in sexual reproduc-
tion that the general facts are so similar in both types of
organisms. If many facts in each kingdom can be included
in the Mendelian conception of heredity, the probability
that it is a truth of universal scope increases by geometrical
progression. Let us see whether or not this is true.

Let us examine first a simple case of monohybridism,
i.e., a case where the parents differ by but one character.
Such a character distinguishes sweet corn from starchy corn.

80 Heredity and Eugenics

The wrinkled condition of the seeds of sweet corn results
from an inability to mature starch grains. The starchy
corns, as the name indicates, possess this feature. One
may say, therefore, that the germ cells of starchy and of

EE
4
|

3

23

Fic. 39.—Segregation of starchiness and
non-starchiness in maize. Above parents and
F, gencration, in center F; generation, below
I, generation,

swect corns are differ-
entiated by the pres-
ence and the absence,
respectively, of the
ability to transmit
starchiness (Fig. 39).
In the higher plants
as in animals the gam-
etes or germ cells are
simplex in character.
Two germ cells, one
male (from the pollen)
and one female (in the
ovule), fuse to form the
duplex cell or zygote
that develops into the
plant. The zygote is
the new plant genera-
tion of which the seed
(except the seed coat)
is but a resting stage
of its development.
Starchiness and non-
starchiness (sweetness)
are seed characters.

One can see just what seed characters the plant possesses,
therefore, as soon as the seed is fully developed. When two
gametes both carrying the factor starchiness (S) produce a

Inheritance in the Higher Plants 87

seed, that seed breeds true to the character starchiness.
When two gametes both lacking the factor starchiness
(s) produce a seed, that seed breeds true to the character
non-starchiness or sweetness. The production of gametes
and zygotes may be illustrated thus:

ers (sls) Non-starchy zygote

Male : Female Male 5 Female
gametes gametes gametes 2 gametes

fie Non-starchy
zygote zygote

When a gamete from a starchy strain fuses with a gamete
from a non-starchy strain a hybrid zygote is formed. This
zygote is starchy like the starchy parent because the
presence of the starchy factor from one parent is sufficient
to cause the development of starch. But the gametes, both
male and female, formed by this hybrid or heterozygote, are
not alike. Half of them contain the starchy factor and
half of them are without it. This being true, when the male
and female gametes of the hybrid pair indiscriminately, the
following combinations occur in equal numbers:

Peel ey [eee |e: see ie | se |.

The first term of this ratio, resulting from the fusion of
two starchy gametes, is a starchy zygote that breeds true;
the second and third terms, resulting from the fusion of a
starchy and a non-starchy gamete, are again hybrid in

88 Heredity and Eugenics

character; while the last term, resulting from the fusion of
two non-starchy gametes, is a zygote that breeds true to
non-starchiness. Since the zygotes having the gametic
constitution shown by the first three terms are alike in
looks, the second hybrid generation (F, generation) gives
approximately three starchy zygotes to one non-starchy
zygote. But the three starchy zygotes, though alike in
looks, are different in their breeding capacity. One out of
three breeds true to starchiness; two out of three are hy-
brid and again segregate into starchy and non-starchy in
the next generation. Diagrammatically the process may be
illustrated thus:
Starchy gamete Non-starchy gamete

\_/

s | Hybrid zygote

Gametes
of hybrid s | | 5

Pure Fe ae 4 Pure
starchy Hybrid non-starchy
zygote starchy zygote

zygotes

Inheritance in the Higher Plants 89

In general one may say that when two individuals are
crossed which differ from each other in paired characters,
of which one can usually be interpreted as the absence of
the other, these parental characters reappear in the second
hybrid generation unchanged in vigor and in potency.
The first hybrid generation may be exactly like one parent
in any particular character, in which case that character
is completely dominant; or, the hybrid may be interme-
diate between the two parents in that character, in which
case dominance is incomplete or absent. Of these two
phenomena the behavior of the second hybrid generation
is by far the most important. The parental characters
are reproduced in it in constant ratios; and it is believed
that this could only come about if the factors that represent
these characters in the germ cells of the hybrid occur there
unchanged and in equal numbers. Generalize this view-
point and we have the belief that organisms behave in
heredity as if they were mosaics of character units, each
unit being represented in the germ cell by one or more
factors of unknown nature. These factors are commonly
transmitted independently of one another, and upon them
depend the characters of the individuals to which they give
rise.

Stated in fewer words, the essential feature of Mende-
lianism is the segregation of potential characters in the
gamete in a state of apparent purity, and their recombina-
tion by the law of chance through random mating. The
term ‘‘ Mendelian notation” was therefore used advisedly.
Mendelian notation is a simple interpretation of certain
facts of heredity obtained in pedigree cultures. It is a con-
venient notation and is used much as the element symbols
are used in chemistry. It makes no difference to analytical

go Heredity and Eugenics

chemistry whether or not an atom is a reality, for the
law of ‘‘Definite and Multiple Proportions” upon which
analytical chemistry is based is still valid. In the same
way, it makes no difference whether one regards unit-
characters as actual units and their segregation as com-
plete, or whether one sees in organisms a mutual dependence
between characters and a quantitative or partial segrega-
tion among gametic factors, the notation is useful either
way to make clear the facts of heredity as shown by actual
experiment.

In a simple case such as that which has just been con-
sidered (segregation of starchy and non-starchy seeds), the
mathematical reasoning that led Mendel to his conclusions
can be shown to be correct. In dealing with some 30,000
progeny, I have found that in the F, generation there
were 23,529 starchy and 7,811 non-starchy seeds, a ratio of
3.0031 : 0.9969+ .0066. This is a 3: 1 ratio well within
the probable error. Furthermore, I find that the positive
and negative departures from the 3 : 1 ratio that occur in
individual ears, are exactly what should be expected by the
mathematical theory of error.

In more complicated cases, sometimes there are depar-
tures from the ratio expected normally that can hardly be
explained by the theory of error, yet in such cases one is
warranted in assuming that misunderstood complications
either obscure or modify the action of Mendel’s law.

Since such accurate ratios as that given above cannot
be expected except by absolute division of the gametes into
two kinds equal in number, it is difficult to believe that
there is not real, exact, and complete segregation. This
would be the inevitable conclusion but for the fact that
extracted pure types do not always breed true as they

Inheritance in the Higher Plants QI

should. An example of this kind has arisen in connection
with the character under discussion. Among many thou-
sand non-starchy seeds that breed true after having been
extracted from a cross, one occasionally appears which is
semi-starchy and transmits this character. What is the
explanation of this phenomenon? The aberrant indi-
viduals are too few to support any theory of partial segre-
gation yet devised. Is it not more logical to believe that
the dominant character has been formed anew? It may be
asked why, if a new character is formed, does it happen to
be the character with which we were previously dealing
rather than some other character? It might be answered
that other characters do sometimes arise. I believe, how-
ever, that a more satisfactory answer can be given. Proto-
plasm undoubtedly differs chemically in distinct species,
and various chemical compounds have individual tenden-
cies toward certain specific reactions. Each species of
organism may therefore have certain paths of least resist-
ance along which variations tend to go. In maize one path
appears to lead to the production of starch (Fig. 4o).
Many characters in the higher plants have been shown
to be inherited as simple monohybrids. Color has been
a favorite subject and its transmission in over thirty species
has been more or less clearly determined. The list of
structural characters investigated is also large. It includes
such different things as tallness and dwarfness (peas and
beans), hairiness and glabrousness (various species), beard-
less and bearded ears (wheat), much-serrated and little-
serrated leaves (nettles), two-celled fruit and many-celled
fruit (tomatoes). A criticism has sometimes been raised
that most of these characters are morphologically unim-
portant. In a measure this criticism is valid, yet there is

92 Heredity and Eugenics

a good reason for its truth. The mechanism of the heredi-
tary transmission of any character can only be demon-
strated when two “crossable” varieties differ in this
character. The characters most important to a species are

Fic. 40.—Starchiness in an extracted recessive. On either side normal
segregates, in center semi-starchy ear grown from non-starchy seed.

characteristic of the species. No individual is without
them; and this being true, the method of their inheritance
must remain unknown. It is often impossible even to tell
whether there is a single or a complex set of factors con-

Inheritance in the Higher Plants 93

cerned in the hereditary transmission of a character. Com-
plexity shows only when the two parents differ in several
factors involving the same character. If they differ by
only one factor, inheritance may appear to be very simple;
but crosses between other individuals similar to the former
in appearance may show an entirely different state of affairs.
A very good illustration of what is meant by this statement
is the inheritance of the purple color of maize that occurs
in the single layer of cells immediately beneath the hull or
pericarp—the aleurone cells (Fig. 41). When an individual
of a variety containing the purple color is crossed with
certain white varieties, the hybrid is purple, showing dom-
inance of the purple character. The second hybrid genera-
tion produces three purple seeds to one white seed. Since
this is the normal monohybrid ratio, one would suppose
that the character in question is simple. This is only
apparently the case, however, for when the same purple
variety is crossed with other white varieties the ratio of
purple to white seeds is such that one knows the varieties
must have differed by two gametic factors affecting the
development of the purple character, instead of one. In
order that this matter may be made clear, the dihybrid
ratio must be explained.

The dihybrid ratio is that obtained when the parents
differ by two character pairs. It is the algebraic product
of two (3+1) ratios. The chances are }X{=,", that the
two dominant or presence characters occur together, $X}=
;3, that the dominant character of the first pair meets the
recessive or absence character of the second pair, +X2= 3,
that the recessive character of the first pair meets the
dominant character of the second pair, and +X}=,', that
both the recessive characters occur together. If we let the

o4 Heredity and Eugenics

two pairs of characters be represented by A and a and B
and 6 the ratio of the occurrence of types in the F, gener-
ation is -l-f+2 fataa and BB+2Bh+5b when considered

LZ fg il o CE A z (tA Ceca)

Fic. 41.—Inheritance of purple aleurone cells. Ear 1 a pure extracted
purple, ear 2 monohybrid with 3 to 1 ratio, ear 3 dihybrid with 9g to 7 ratio, ear 4
a pure extracted white.

separately. If one wishes to obtain the probable ratio
when both characters are considered together he has but
to multiply the two series together. This gives the prod-
uct AABB+ AAbb+aaBB+aabb+2AABb+ 2aaBb+2Aa

Inheritance in the Higher Plants 95

bb+2AdaBB+4AaBb. Since heterozygotes resemble homo-
zygotes in appearance in the cases of complete dominance,
however, the visible appearance of the F, generation is
GAG + 2A > 308 * nab.

Perhaps the easiest method of showing the combinations
of gametes in Mendelian inheritance is by the use of four
squares multiplied once by four for each character pair.
In the case of dihybrids sixteen squares are necessary.
Write each possible gametic combination of the male cells
in each horizontal row of squares, AB, Ab, aB, and ab.
Next write the same combinations for the female gametes
in each vertical column of squares. This gives all the
zygotic combinations possible.

We are now ready to see just why one cannot tell whether
he is dealing with a simple or complex state of affairs in
Mendelian inheritance. In the monohybrid ratio of purple
and non-purple aleurone cells of maize the segregation in the
F, generation is:

P p

P

P p
p

Three purples to one non-purple are produced.

In the dihybrid ratio when other white varieties were
used as one of the parents, nine purples to seven non-purples
were produced. This simply means that two factors are
necessary to produce the purple color. These factors may

96 Heredity and Eugenics

be represented by the lettersC and P. The gametic formula
of the purple variety is CP; the gametic formula of these
particular white varieties is cp. If either C or P is absent
from the zygotic formula of F, then the zygote is white as
is shown in the diagram.

DIAGRAM ILLUSTRATING INHERITANCE OF PURPLE ALEURONE
CELLS IN MAIZE WHEN TWO FACTORS ARE CONCERNED

CP cp | cP CP
CP Cp cP cp
Purple Purple Purple Purple
Cp Cp Cp Cp
CP Cp GP cp
Purple White Purple White
cP cP cP cP
CP Cp cP cp
Purple Purple White White
cp cp cp cp
GP. Cp GR. cp
Purple White White White

The formula of the purple is therefore CCPP, but whites
with formulas CCpp, ccPP, and ccpp may exist. When the
whites have formulae CCpp or ccPP they give monohybrid
ratios when crossed with the purple, but when they have
the formula ccpp a dihybrid results.

This illustration shows both why one cannot tell just
how complex a character is, and why characters essential
to the species cannot be analyzed.

These cases of Mendelian inheritance are types. Other

Inheritance in the Higher Plants 97

cases may be more complex in appearance but this is a sur-
face complexity only. They yield to similar analyses when
they are properly understood. This complexity in appear-
ance has many times made cases appear to be exceptions
to Mendel’s general law. Various ratios have been obtained
that were seemingly inexplicable, but these one by one have
been found to be merely variations of the simple ratios that
we have just discussed. Perhaps the most interesting of
these aberrant ratios are those cases of heredity dealing
with latent characters. We will consider some of these
briefly as examples of the various manifestations which are
found in the hereditary transmission of plant characters.

One of the most important classes of latency we have just
discussed. It is called latency of separation. Where a
character exists through the interaction of two factors,
these factors may at some time become separated, that is,
possessed by different individuals. When this occurs the
character is apparently lost and does not again appear
unless two individuals bearing the complementary factors
are crossed. This is the explanation of the old phenome-
non of reversion after crossing. It was first explained by
Bateson from experiments with sweet peas. He found that
two white varieties yielded the purple color of the wild
sweet pea when crossed. In the same way I have found
that the white seeds in the dihybrid ratio of 9 : 7, shown
by the purple X non-purple cross of maize varieties, give
purple seeds when crossed at random. The non-purples
exist in the following ratios:

1 CChp
\; Copp
TOT OOP
le CCL Dp
I ¢c cpp

98 Heredity and Eugenics

When crossed at random, there are 7X6=42 possible com-
binations of which 24 give all white seeds and 18 give some
purple seeds. Of these 18 ears there would be on the aver-
age 2 pure purples, 8 with purples and whites in a ratio of
tr: 1,and 8 with purples and whites ina ratio of 1: 3. Such
results have been obtained experimentally and examples
are shown in Fig. 42.

Tic. 42.—Reversion due to latency of separation. Purple seeds produced by
crossing whites. Ear 1, 1 to 3 ratio; ear 2,1 to £ ratio.

A different kind of latency is simply invisibility of a
character due to some obscuring factor which may be
removed by means of a cross in which the latter is absent.
This latency is called that of hypostasis, a hypostatic char-
acter being one which is obscured by another called the
epistatic character. There are instances where this epi-
static character may be removed mechanically and the
hypostatic character revealed. Such a one is the red-eared
maize, for the color there lies in the hull or pericarp. This

Inheritance in the Higher Plants 99

may be scraped off to show the color of the true seed
which may be either yellow or white. In most cases,
however, the relations are physiological and the hypostatic
character can be demonstrated only by crossing. For
example, the maize with purple aleurone cells carries also
a factor for red aleurone cells which can be demonstrated
only by crossing it with a variety in which the purple factor
is absent. There is produced an F, generation with a ratio
of 27 purples : 9 reds : 28 whites.

This statement may appear to be a direct contradiction
of the interpretation of the inheritance of purple aleurone
color that has just been given. In reality it is merely
another illustration of the fact that one can never know
definitely the factors involved in producing a character, for
he can never feel assured that the parents involved in the
cross have differed in all the factors that affect its develop-
ment. When the purple was crossed with the white and a
ratio of 9 purples : 7 whites obtained in the F, generation,
it was proper to interpret the purple parent as PPCC
and the non-purple parent as p pcc. But when the purple
is crossed with another non-purple and a ratio of 27 purples:
g reds : 28 whites is obtained in the F, generation, it is clear
that a different interpretation is necessary. The purple
parent has the formula P P R RCC and the white parent
the formula p prrcc. The zygotic formula of a pure red
seed is RRC C and of a pure purple seed is PP RRCC,
but a seed with the formula P PCC is white. In other
words, the factor P produces the visible purple color only
in the presence of factors C and R. The purple has always
the constitution P P R RCC ; when it is crossed with whites
having the characters PP RRcc or PPrrCC, a ratio
of 3 purples : 1 white is obtained in F,; when it is crossed

100 Heredity and Eugenics

with a white having the composition P Prrcc, a ratio of
9 purples : 7 whites is obtained in F,; when it is crossed
with a white having the composition p prrcc, a ratio of 27
purples : 9 reds : 28 whites is obtained in F,,.

It is possible that another factorial difference may yet
be found which will show this character to be still more
complex. Baur, Bateson, Saunders, and Gregory have
shown that the sap colors of the flowers of Antirrhinum, of
Lathyrus, of Matthiola, and of Primula belong to this type
and are yet more complex. But this does not affect our
general conception of the inheritance of the colors in the
least.

Sometimes latent characters very similar to this are due
to the presence of a second inherited factor which does not
allow the first character to develop. This is called latency
due to inhibition. Similarly there may be inherited char-
acters which help to a more perfect development other
independently transmitted characters. This is undoubtedly
an important phase of Mendelianism for although we may
conceive factors as holding within themselves the poten-
tialities of certain characters, they undoubtedly are influ-
enced in their development by the development of other
inherited characters. One may imagine that factors repre-
senting characters may be transmitted but are either not
expressed at all or are developed to a limited degree owing
to the presence or the absence of other inherited characters
that affect this development.

Perhaps this theoretical conception may be made plain
by an example of what has been termed latency of fluctua-
tion. In this class are included characters which are poten-
tially present in an organism but which may develop to a
greater or less extent due to varying influences which sur-

Inheritance in the Higher Plants 101

round them. There is a red color in the pericarp or hull of
the maize seed which is transmitted as a simple Mendelian
monohybrid when crossed with a variety in which the
character is absent, but the color develops to its full extent
only in bright sunlight. When a black bag is placed over
the young ear the color does not develop at all, yet such a
colorless ear will transmit the color as well as if that ear had
developed in bright sunlight. One may easily see then
how he might be deceived in the classification of such indi-
viduals and thereby draw wrong conclusions regarding the
inheritance of the character.

Though the example just given is one of latency of fluc-
tuation, it really consists in the character being partially
inhibited by absence of light. One may see from it, how-
ever, that there can be real latency of inhibition through the
influence of inherited factors that affect the development of
independent characters.

We have hitherto considered characters that seem to be
transmitted independently of one another. Let us now
spend a moment in discussing characters that appear to be
either coupled or antagonistic to each other in their trans-
mission. Some very interesting results on this subject
have been obtained by Emerson (Fig. 43). There are
maize varieties which are red in both the pericarp of the
seed and the cob. When one of these is crossed with a
variety in which color is absent in both the pericarp and
cob, the second hybrid generation produces three ears like
the colored parent to one ear like the white parent. One
might suppose that the color in pericarp and in cob was due
toa single gametic factor. This can hardly be the case, how-
ever, for there are varieties with red pericarp and white cob
and varieties with white pericarp and red cob. When two

102 Heredity and Eugenics

such varieties are crossed together the first hybrid genera-
tion produces ears with red pericarp and red cob like
the colored variety in the previous cross. In the second
hybrid generation, however, we find produced 1 red

Heine

n™a8

SHA25D
ALS

240

nS)
Oo nee

Ae.

2v

@
[iad |

: DaVOQy.nV
Dpem On
eee te

2%
MS

Fic. 43.—Red pericarp and red cob coupled in inheritance. (Photo by
Emerson.) F, generation shown. Ears 1, 2, 3 with red cob and red pericarp,
eat 4 with white cob and white pericarp.

pericarp with white cob: 2 red pericarp with red cob: 1
white pericarp with red cob. The first and third classes
breed true to their conditions, but the second class proves
to be always heterozygous and breaks up in the next gen-
eration as did those with similar characters of the first
hybrid generation.

Inheritance in the Higher Plants 103

Without going into the theory of this phenomenon it is
apparent that in the first case red pericarp and red cob

cé e

Bissccse
sh Coe
puGQgGs
@e, ,

3

c= )
~

-—

"s

ak
re
4

UGG
a

0ae

)

ge > wu é

ae és
pee

A

Tic. 44.—Red cob and red pericarp antagonistic in inheritance. (Photo
by Emerson.) [2 generation shown. Ears 1 and 4, like parents, are pure types.
Ears 2 and 3 are heterozygous.
were not produced by a single factor in the usual sense, but
by two individual factors coupled in their inheritance. In
the second cross the two factors were not coupled; in fact

104 Heredity and Eugenics

they were just the opposite, they were antagonistic to each
other so that no pure types were produced having red peri-
carps and red cobs (Fig. 44). This is an example of a fea-
ture which is probably very widespread in the plant world,
but of which we at present know little. It is cited for two
reasons; first, to show that characters may at one time be
antagonistic to each other and at another time coupled
together, and second, to show that one is not able to say
beforehand whether a manifestation of a character in
several organs is due to one or to several separately
inherited factors.

Leaving out of consideration sex-limited inheritance of
which little is known in plants, we have now briefly gone
over simple type cases of some of the most important present-
day Mendelian knowledge; but we have considered only
crosses in which the potential character or characters are
present in one parent and absent in the other. At least
they behave that way and may reasonably be so interpreted.
Such differences between parents are qualitative, but most
differences between parents are quantitative and give an
apparent blend in the first hybrid generation. Nearly all
cases where varieties differ in the size of their organs are
of this kind. Can such phenomena be interpreted by
Mendelian notation? I believe they can. One may think
of a factor for a character being present in the germ cell
not only once but twice or even a greater number of times.
If these factors are transmitted independently and are not
paired with each other, but each with its own absence, one
may very easily interpret size inheritance. For example,
when a certain dent variety of maize is crossed with a flint
variety as shown in Fig. 45, an intermediate condition is
obtained in the first hybrid generation. In the second

Inheritance in the Higher Plants 105

hybrid generation one ear like each original parent is
obtained out of every sixteen instead of every four (Figs.
46, 47). This inheritance is therefore dihybrid in charac-
ter. In lke manner, a higher number of transmissible fac- -
tors may affect the development of what is to the eye a
single character.

Since dominance is not an essential feature of Mendeli-
anism, size characters may show intermediates or blends
in the first hybrid generation and still fulfil the essential
conditions of Mendel’s law by recombining in such a fashion
as to produce individuals like either parent in the second
hybrid generation provided a sufficiently large number of
individuals to allow for the recombination of several factors
is grown in that generation. Such recombinations do occur
and can be shown by experiment. For example, the small
variety of corn, Tom Thumb, when crossed with a larger
variety like the Black Mexican (Fig. 48), gives a first hybrid
generation that is intermediate between the two parents.
One may call this a blended condition; yet if there were
blended inheritance this condition would be transmitted,
while if Mendelian recombination occurred, sizes compa-
rable to either parent would be obtained in the second hybrid
generation. Such extremes were obtained as is shown in
the figure.

If the possible Mendelian interpretation of quantitative
characters has been made clear, the statement that Men-
del’s law is probably universally applicable where sexual
reproduction occurs will not seem rash. There are still
some apparent exceptions to the law, but they are so few
that one may well believe we simply do not know how to
bring them into line and not that they are actual exceptions.
Of course it is quite likely that there are other laws which

106 Heredity and Eugenics

modify the action of Mendel’s law in a manner similar to
that in which the physical laws holding good under theo-
retical conditions are modified under conditions existing
in nature.

Granted, then, that Mendelianism is broad in scope,
could it have been of great value during the progress of

ty
eo
yo
e
or
pl
win
ee.
Cd
Se
i
&
Ud
eB

Fic. 45.—Inheritance of physical condition of endosperm in maize. Parents
and F generation shown.

evolution? That it should have been of great value to
very primitive forms of life does not seem possible, and even
after the origin of sex its precise importance is somewhat
problematical. It has disposed of one of the main criticisms
against Darwin, at least, that of the swamping effects of
intercrossing upon newly arisen characters that are an advan-
tage to the specics. Since characters are segregated as units

107

Inheritance in the Higher Plants

Flint-

SRIBHEL>

iyi

in maize.

ETT a tntitee, A,
RAPS 52 NSDI PEDROS) DEER ORESS ATRL:
DOS RAS GORTESEDODCEERSTIO TN EUS

ao

west, &o8

iH Oo ay 9 0G8 }
=: sash {atts tra
ah 28) Sys: os .

id iad

phipid esse

wetintie *

Ukiah

ESO Lgs Oiod | Fy

eee

cc qeenstetee

Fic. 46.—Inheritance of physical condition of endosperm

like F; segregate above and I’; progeny below.

(aa

|

Dent-

Fic. 47.—Inheritance of physical condition of endosperm in maize.

like F. segregate above and F; progeny below.

108 Heredity and Eugenics

in the hybrid it matters not whether they are dominant
or recessive or whether there is no dominance, there will
be no dilution from intercrossing. A second and more
important advantage, due to the operation of the law,
results from the recombination of characters. Characters
may be transmitted as units and chance recombinations
of these characters may occur without anything really new
to the organism being formed, yet in this recombination
the organism as a whole may be better fitted for its environ-
ment than ever before. And this is giving recombination
its smallest value, for, however independently potential
characters may be transmitted, no one believes that a
developing organism is simply a mass of independently
developing unit-characters. The characters of an organ-
ism are more or less dependent upon one another in their
expression, and in this interdependent development the
greatest possibility for good recombinations occurs. Theo-
retically nothing new may result from the mere act of cross-
ing, but practically a new combination of old characters
may result in something quite different. A little thought
and the use of chemical analogies where the same mixtures
produce different chemical results under different physical
conditions, show the importance of this conception to Men-
delian theory. Yet it is not necessary to believe the cur-
rent teaching that one has only new recombinations and
not new characters to deal with in crosses. The theory
that several germ-cell factors may be due to produce the
same character gives us a reasonable and orthodox explana-
tion of the origin of characters really and truly new by the
interaction of gametic factors that are old. For example,
let us suppose that in a certain species with a petioled leaf
there is a variety which has the presence of factor A pro-

Inheritance in the Higher Plants 109

(00x) F

Fic. 48.—Inheritance of length of ear in maize. Parents above, F; genera-
tion in center, F, generation below. Class sizes in centimeters with number of
variates below.

IIO Heredity and Eugenics

ducing a slight tendency toward a sessile leaf. Factors B
and C may ultimately arise as modifications of factor A.
Each alone may produce the same result as A; yet if they
are transmitted independently, are not allelomorphic to
each other and are cumulative in their action, a sessile leaf—
a new character—is produced.

The remainder of this chapter will be devoted to a con-
sideration of Johannsen’s genotype conception of heredity.
It may seem as if Mendelism has been dropped abruptly to
take up anew subject. Thisisnot the case. The genotype
conception of heredity is merely an acknowledgment of the
universality of Mendelism.

Johannsen, who developed the genotype idea, found
that some variations were not inherited. These were the
general variations in relative perfection of development of
parts, caused by varying physical and chemical conditions
of environment. This is only an acceptance of Weismann’s
theory that inheritance is from germ cell to germ cell, and
that ordinary environmental influences affecting the body
only are not transmissible. Of course both Weismann and
Johannsen acknowledge that certain changes in environ-
ment may produce structural modification of the germ
plasm and therefore a heritable variation, but whether the
heritable variation produced is ever identical with the
adaptive response of the parent organism is still in dispute.

If this contention be true, it follows that the hereditary
characters of an organism are determined by the consti-
tution of the fertilized egg from which it came. Johannsen
denotes the sum total of the gametic factors making up a
zygote by the word genotype. If two individuals possess
identical gametic factors, they are members of the same
genotype. Of course no one can describe a genotype in

Inheritance in the Higher Plants III

concrete terms. It is a theoretical, a philosophical, concep-
tion. If one crosses two individuals, the genes or gametic
factors common to each breed true. He can obtain an
idea of the behavior in heredity of those factors only which
are not common to the two parents. These factors segre-
gate and recombine in definite proportions. They follow
Mendel’s law. The genotype conception of heredity is
therefore the conception that duplex or homozygous gametic
factors are due to produce identical results within the
limits of variability imposed by external conditions and
by the influence of other independent gametic factors during
ontogeny, no matter what is the appearance of the indi-
vidual from which they were derived. This is a strict
Mendelian conception of heredity extended to the organism
as a whole.

We need not go into the many lines of work that support
the genotype theory. Considered in a broad way I believe
no reputable modern work is irreconcilable to it, although
some authors do not so interpret their work. All modern
plant breeding is in its support, for the principle of Vilmorin,
the progeny test, which is the basis of all modern selection
work, is founded upon the same conception. In naturally
inbred plants, one has commercial strains which are mechani-
cal mixtures of near-homozygotes, and can be immediately
isolated. In naturally cross-bred plants or in bisexual ani-
mals, one has physiological mixtures, that is, hybrids or
heterozygotes, from which it takes somewhat longer to iso-
late particular strains that are genotypically homozygous in
respect to certain characters, but in which the separation
is accomplished by the same means—the breeding test.

In the theoretical homozygous genotype transmissible
variations may occur, for no one believes protoplasm

Tre Heredity and Eugenics

unchanging. Such a conception would be mechanical and
not biological. These changes must affect the germ cell
structurally to be inherited. They may be large, they may
be small. We may call them mutations with DeVries, or
we may use the simpler and broader term, inherited varia-
tions. When they occur, new varieties may be isolated
in which they are present, and these may be considered
to be relatively permanent as compared with the non-
inherited fluctuations that continually occur due to varying
environment.

One may question the stability of unit-characters as does
Castle, but I cannot see how this affects the truth of the
genotype conception as a help toward an idea of the process
of heredity. Stability isa relative thing. Why is there not
a scale of stability in biology even as in chemistry? Many
unit-characters are high in the scale of stability, others may
be low. Certain characters ordinarily transmitted perfectly
may possibly be modifiable by selection. We might imagine
their factors to be huge chemical molecules, stable as a whole
but modifiable by isomerism or even the dropping off or
adding on of unimportant radicles. This is a smaller issue,
unimportant when compared with the genotype conception
as a whole. The important point as the foundation of the
modern view of heredity I give in Johannsen’s own words:
“Personal qualities are the reactions of the gametes joining
to form a zygote; but the nature of the gametes is not deter-
mined by the personal qualities of the parents or ancestors

in question.”

CHAPTER VI

THE APPLICATION OF BIOLOGICAL PRINCIPLES TO
PLANT BREEDING

In this chapter I shall take up the commercial appli-
cation of some of the principles of plant genetics previously
discussed.

The fact must again be emphasized that there are two
kinds of variation:

t. Fluctuating variations, which are due solely to sur-
rounding influences such as better position for develop-
ment or varying fertility of the soil. Such variations, are
not inherited.

2. Inherited variations, which are due to some structural
change in the reproductive cells. These variations may
depend upon environmental conditions for their full devel-
opment but not for their transmission.

Inherited variations possess the only value to the plant
breeder, yet the work of improving plants is rendered a
great deal more irksome by the presence of fluctuations and
by the fact that one cannot tell the gametic constitution of
a plant, that is, its breeding capacity, by its appearance.
The whole problem of the plant breeder is to find, to fix, and
to recombine desirable inherited variations, and to do this
in spite of their tendency to be obscured by fluctuations.
The methods used to accomplish these results will be taken
up presently. First, attention must be called to a physio-
logical phenomenon that may be made a tool of such high
value to the plant breeder that the statement just made
concerning his problem is apparently untrue. This matter

113

TI4 Heredity and Eugenics

is an exception, however—a thing apart from the usual
breeding procedure.

It will be remembered that when a plant receives iden-
tical character factors from each parent, that character is
homozygous and breeds true; but when the plant receives
the character from only one parent, the character is hetero-
zygous and shows segregation in the next generation. This
heterozygous condition, though not fixable itself, since it
always breaks up in the succeeding generation, is a valuable
asset to the plant breeder if properly utilized and a distinct
disadvantage if unrecognized.

The fusion of two gametes into a zygote which is known
as fertilization effects two very different results: first, a
union of the hereditary factors possessed by these gametes;
second, a stimulation to the cell division necessary for
normal development. Probably in every case where fer-
tilization can take place at all there is a certain amount of
this stimulus to development, but the fact of especial interest
to plant breeders is that this stimulus is generally far greater
in a hybrid or heterozygote than it is in a pure-bred or
homozygous individual. The stimulus is simply toward
greater and quicker cell division and affects only size and
rapidity of maturity.

The tobacco genus (Vicotiana) furnishes an admirable
type illustration of the stimulus due to heterozygosis because
the species are generally self-fertilized under natural con-
ditions. The stamens and the pistil are about the same
length, and since the pollen is usually shed before the flower
opens, self-pollination must occur unless foreign pollen is
carried to the unopened bud by insects. When varieties
of the common tobacco NV. tabacum are crossed together,
the first hybrid generation is nearly always from 5 to 50

Application of Biological Principles to Plant Breeding 115

per cent taller than the average of the parents. The
hybrids also have somewhat larger leaves than the average
of the two parents although the number is generally inter-
mediate. This statement is true in general for crosses
between the varieties of most other species. When true
species are crossed, however, the behavior of the first hybrid
generation is somewhat different. Sometimes there is a
great increase in vigor. WN. tabacum X N. sylvestris gives
hybrids that are nearly double the average height of the
parents. NV. tabacum X N. alata, on the other hand, gives
hybrids that are less than one-fourth the size of the smaller
parent. Both of these crosses are sterile, so that the differ-
ence in behavior cannot be correlated with sterility. One
can simply say that species vary in their affinity to cross
with other species. All gradations are found, from those
that produce full quotas of viable seed, to those where only
an occasional seed is found or where the capsule simply
develops without the formation of seed. And in general
the additional vigor of the first hybrid generation increases
with the ease of making the cross. With perfect ease of
crossing the stimulus is roughly a function either of the
number or of the kind of character pairs for which the
individual is heterozygous.

Species naturally self-fertilized lke tobacco or wheat
must get along without the increased vigor due to hetero-
zygosis. One notices the difference only when artificial
crosses are made. Species which in nature are cross-
fertilized, however, are usually heterozygous for so
many characters that one does not think of their vigor as
being largely due to this cause. The fact is only brought
to notice when the species is self-fertilized artificially,
for this tends to isolate homozygous strains (Fig. 49).

110 Heredity and Eugenics

Ii, for example, a commercial variety of maize is self-

(2xD F
SUZS bu peracre
S

Nod,

ae bu per acre

Nod,
ATT bu peroere |

Fic. 49.—Genotypical strains of maize withdrawn from a commercial variety by inbreeding and their behavior when crossed

fertilized for a number of
generations, the plants
tend to become homo-
zygous, to lose the vigor
due to heterozygosity
and to become smaller
and less productive.
This loss of vigor was
for years interpreted as
the direct effect of self-
fertilization. Now we
know that it is simply
the withdrawing of pure
strains from hybrid com-
binations. In a few
generations the strains
become practically pure
and the loss of vigor
ceases. Some strains of
maize still yield remark-
ably well after many
generations of self-
fertilization. Other
strains are so poor that
they can scarcely be
kept alive. In fact it is
evident that they are
kept alive merely by
the increased vigor of
growth due to continual
natural hybridization
with other strains.

A pplication of Biological Principles to Plant Breeding 117

Since all commercial methods of selection in maize, as
well as other naturally cross-bred species, have as their
ultimate goal the isolation of good homozygous strains (for
this is what the words “selection to type” mean), it is quite
evident that the longer selection has been carried on the
more of this stimulus due to heterozygosity or hybridity
is lost. No method of breeding naturally cross-bred species
therefore, where size and total yield are the main objects,
is proper unless these facts are taken into consideration
and the methods so modified as to utilize them. This is
done by growing only the first hybrid generation of crosses
between good strains. Nor is it alone in wind-pollinated
field crops, such as maize, that these methods are useful.
Horticultural crops such as tomatoes and eggplants can be
grown from hand-hybridized seed with a profit greatly
exceeding the extra cost of its production. It may be that
even certain trees can be hybridized to advantage for
undoubtedly Burbank’s quick-growing walnuts are due to
this phenomenon. Furthermore, it accounts for the fact
that all asexually propagated crops worthy commercial
supremacy, such as grapes and potatoes where yield is the
object of prime importance, are always hybrids. Their
mode of commercial propagation is such that the first
hybrid generation can be indefinitely prolonged.

It is not easy to leave this subject without mentioning
the important réle which this growth stimulus due to
hybridity may have played in the evolution of the higher
plants. In self-fertilized species, for example the violets,
the fact that the hybrid between two nearly related strains
was more vigorous than either parent type would have
given it such an advantage in the ordinary struggles for
existence against inhospitable environment, that the chances
are greatly in favor of its surviving to produce recombi-

116 Heredity and Eugenics

nations of the parental characters in the next generation.
And there is always the chance that new recombinations of
parental characters may prove better fitted to survive than
the old combinations. In cross-bred species the stimulus
of hybridity holds a still greater advantage since even
homozygous strains that are weak and could never exist
alone, may, through combination with other strains, be
kept in existence as heterozygotes. For example, one finds
in maize literally thousands of genotypic strains in a single
commercial variety. Many could not exist alone, yet they
continue to exist in commercial varieties through hybridity
and their existence may be proven by their being partially
withdrawn by inbreeding. Such strains may have great
possibilities in certain combinations as is shown in Fig. 49.
In inbred or self-fertilized species such as tobacco, however,
strains weak in themselves perish and are lost to sight
because there is no probability of their being hybridized
and given a chance of showing their power in combination.

This one phenomenon, alone, may account for the
commonness of cross-fertilized species and the rarity of self-
fertilized species, since it can be shown that there is no evil
effect due to inbreeding per se.

Passing now to the work more generally included in plant
breeding, we find that commercial methods fall naturally
into two classes, hybridization and selection. They are
not really thus separable since one must use selection after
hybridization, but in the first category are classed all
cases where man produces hybrids artificially. The main
object of hybridization is the shuffling of unit-characters
in the first hybrid generation and their recombination and
fixation in succeeding generations. The object of selection
is to withdraw from mechanical mixtures or from physio-

A pplication of Biological Principles to Plant Breeding 119

logical mixtures due to hybridity, strains characterized by
desirable new variations.

Practical procedure in hybridization naturally varies
somewhat depending upon the exact object in view. I will
endeavor to illustrate the following phenomena as those of
most importance: (a) Recombinations of desirable char-
acters and their fixations, including the production of
blends; (b) production of desirable combinations in the first

Fic. 50.—Buds of Nicotiana tabacum showing time and method of castration

hybrid generation and their continuation by asexual propa-
gation; (c) production of fixed first generation hybrids.

If one is to begin at the real beginning in this discussion,
he should spend a moment in describing the mechanical
operations of crossing (Fig. 50). There are three important
steps. First it must be determined by experiment what
environmental conditions are best suited for normal seed
production. Second, an intimate knowledge of the flower-
ing habits and flower structure should be gained in order

120 Heredity and Eugenics

that the flowers may be castrated at the correct time without
injury and properly protected from foreign pollination until
the time for hybridizing. Third, care must be exercised in
applying the pollen of the proposed male parent, for both
premature and delayed pollination inhibits seed formation.

The precise conditions under which a cross should be
made to be the most successful are not easily determined.
The proper preparation of the breeding plot even before
the plants are grown is necessary. One takes it for granted
that on most soils some fertilizer will be used, for the plants
must be normal to seed well. The three essential elements
of soil fertility are nitrogen, potassium, and phosphorus,
and to get the best results compounds of these elements
must be present in proper proportions. First, available
potassium must be present in quantities sufficient for the
normal production of healthy roots, leaves, and stems, and
a moderate excess will not be harmful. If nitrates are
present in excess, however, vegetative growth will be over-
stimulated and seed production will be small. A lack of
phosphorus will produce the same effect upon seed pro-
duction, but for a different reason. Phosphorus is an essen-
tial constituent of the proteid compounds found in large
quantities in the seed. If the plants are to be in the best
condition for the production of good seed after crossing,
therefore, the soil should contain just the right amount of
nitrates for a normal vegetative growth, and a generous
supply of potash and phosphates. The exact amounts
must be determined by experiment for each soil and each
species of plant.

External conditions that are also under partial control
of the breeder are available moisture through irrigation and
sunlight by proper spacing or artificial shading.

A pplication of Biological Principles to Plant Breeding 121

Other necessary knowledge that can be obtained only
from experience is, which are the best flowers on the plant
to serve as parents of the cross and what is the proper time
for their pollination. For example, in the grasses the first
flowers that appear usually form larger, healthier seed than
the later blossoms. In most of the Solanaceae, the petunias,
browallias, etc., the exact opposite is true. The time when
the individual flower is most receptive to pollen is even more
narrowly limited. Both premature and delayed pollina-
tion is the cause of many failures and the optimum time
should be accurately determined. Having exercised these
precautions, it remains to study carefully the structure of
the flower in order that it may be emasculated, i.e., the
anthers removed before the pollen is shed, with sufficient
adroitness that neither the anthers shall be opened nor the
parts of the pistil injured. Only a few buds upon a single
flower spike should be operated upon if they are to be given
the best chance of development. If the buds are very
small and some pollen unavoidably reaches them, it may
be washed off with comparative safety with a dental syringe
if done immediately. It is often recommended that the
calyx and corolla be cut away when emasculating. This
should be avoided if possible and the floral envelopes left
as a protection to the pistil. After emasculation the buds
should be protected from foreign pollen until time for
pollination, and again after pollination at least until the
fruits have begun to form (Fig. 51). This protection may
be an ordinary paper bag when the crossing is done in the
field. It may be used with a plug of cotton around the
mouth if special precautions are found necessary. In the
greenhouse a square of thin celluloid rolled around the
flower and caught with two rubber bands, each end being

122 Heredity and Eugenics

protected with absorbent cotton plugs, is a better device.
It gives excellent protection and allows transpiration,
But I must pass from the technique of hybridizing to

Vic. 51.—Impaliens sullani showing protection of castrated buds in green-
house.

the results. They are much more interesting. As has
already been stated, desirable horticultural novelties are
obtained most frequently by crossing two plants which

A pplication of Biological Principles to Plant Breeding 123

differ in several transmissible characters. The first hybrid
generation may be as uniform as one of the pure varieties,
but in the second hybrid generations all possible combina-
tions of the characters of the two parents are obtained
provided a sufficient number of individuals have been
grown. Among these combinations many new and desir-
able types may be found. Some of them are pure types;
some are heterozygous and will again segregate. Since
homozygous and heterozygous types are found which are
exactly alike in appearance, the only way to determine
which plants are pure is to self-fertilize desirable individuals
and raise a third generation. For example, 1. alata,
a species with large white flowers, when crossed with
N. forgetiana, a species with small red flowers, gives
hybrids that are very uniform in all their characters. The
flowers are intermediate between those of the parents in
size, and are red in color. In the second hybrid generation,
there are 16 visibly different color types. Among these
there are really 81 classes, including those both pure and
hybrid. It is therefore necessary to grow seed from many
self-fertilized plants for another generation to be certain
of getting pure strains of each type. But having done this,
the pure types continue to breed true in spite of the mixed
ancestry.

This method is typical of the manner in which floral
novelties are produced. So many varieties carry latent
characters that one is always likely to obtain new things
in crosses. Results of greater economic worth, however,
are probably obtained by combinations made for a definite
purpose. A beautiful example of such work is afforded by
the experiments of Biffen. English wheats have long been
known as highly productive varieties, but they are very

14 Heredity and Eugenics

susceptible to a fungus disease called rust, and do not make
first-class bread on account of the low percentage of gluten.
After many importations, wheats resistant to rust and
high in gluten content were obtained, but these were not
profitable because of their low yields. Biffen then went
to work to analyze the
transmissible characters
of the wheats into Men-
delian factors by a large
series of crosses. This he
was able to do. The rest
was easy. He has now
produced by hybridiza-
tion wheats that com-
bine the desirable
qualities and which lack
those disadvantageous
to the grower and the
baker.

Sometimes a very sim-
ple recombination is of

very great commercial
value (Fig. 52). The so-
called Havana type of

Fic. 52.—Nicoliana tabacum variety Wrapper tobacco grown
“Havana.” A stocky habit of growth with in the Connecticut
about 20 large leaves. ‘

River valley has large
leaves and a short stocky habit of growth. It produces
18-21 leaves. There is another type from Sumatra which
has tall habit of growth with about 26 comparatively
small leaves. These two types were crossed by Shamel.
From this cross a new type called the Halladay has been

A pplication of Biological Principles to Plant Breeding 125

produced having the greater number of leaves of the Suma-
tra parent and the stocky habit of growth and large leaves
of the Havana parent (Fig. 53). The first interpretation
of this result was that an entirely new variation had appeared
for the Sumatra does not
usually have as many as
26 leaves. The writer has
been able to show, how-
ever, that the actual strain
of Sumatra used as the
parent had an average of
26 leaves, and data have
now been collected which
indicate that the new
variety is a simple recom-
bination of the characters
possessed by the two par-
ents giving a strain averag-
ing 30-50 per cent greater
yield than the old Havana
variety (Fig. 54).

In a similar way Orton
has combined the edible
quality of the watermelon
with the resistance to wilt of Fic. 53.—Nicotiana tabacum variety
the citron or stock melon; “Sumatra.” A tall habit of growth with
Webber has combined the “"M* 7° small aves
fine, long, strong lint of the sea-island cotton with the large
bolls and productiveness of the upland cotton; Price has
made many new combinations in tomatoes; and von
Riimker has produced numerous valuable varieties of rye
and barley. So the list might run on and on. Hundreds

120 Heredity and Eugenics

of plant breeders are using these methods to produce thou-
sands of new types annually. Most of them are worthless,
nearly all of them are no better than what are already
in commercial use, but the comparatively few that are

Fic. 54.—Hybrid combining the desirable qualities of the “Havana” and

“Sumatra”? varieties.

really superior repay the time and money spent a thousand
fold. I might add that it is the community at large that
is highly repaid, however, for the plant breeder, unlike the
inventor, never gets rich through his productions.

A pplication of Biological Principles to Plant Breeding 127

Recently, accurately controlled investigations have
shown that a strict Mendelian notation will interpret results
that hitherto had been given the name blended inheritance.
For instance, one may cross an eggplant, Solanum melon-
gena, bearing large fruits with one bearing small fruits.
In the first hybrid generation, fruits intermediate in size are
produced. Segregation in the second hybrid generation is
such that plants bearing fruit like either parent can be
obtained if a large number of individuals (several thousand)
are grown. Yet among the F, progeny, intermediates still
occur in large numbers, and from them pure types can be
secured.

Most of the characters hitherto described are qualitative
in nature. They are either present or absent in the differ-
ent varieties. Such characters are generally dominant,
in which case the heterozygotes are like the homozygotes
in appearance. Other characters give heterozygotes inter-
mediate in appearance, owing to incomplete dominance,
but these intermediates can never be fixed. Owing to their
heterozygous constitution they always segregate the paren-
tal characters in the next generation. Size characters or
quantitative characters, on the other hand, are often very
complex. They are due to the interaction of many factors.
For this reason blends may be obtained in the F, genera-
tion that are homozygous for such a combination of game-
tic factors that they always breed true to that condition
(Fig. 55).

Fortunately it is not necessary always to have plants
that breed true to seed. Many commercial plants are
propagated asexually by bulbs, tubers, cuttings, etc.
Here one has a method of growing portions of a single plant
for an indefinite length of time. Fruit trees, bush fruits,

128 Heredity and Eugenics

strawberries, potatoes, pineapples, and many other kinds
of economic plants belong to this category. This is a great
advantage. One can so propagate homozygous strains if he
wishes, but in addition he has a means of utilizing heterozy-
gotes that would not breed true to seed and also of keeping
the greater vigor that ac-
companies heterozygosis.
No better example of
such work can be given
than that of Webber on
citrus fruits. The great
bugbear of the Florida
orange grower is the frost
that occasionally comes,
leaving devastation in its
wake. Webber, therefore,
set himself the definite
problem of producing a
frost-resisting orange. He
made several reciprocal
crosses between the com-
mon orange and the hardy
but worthless trifoliate

Fic. 55.—Intermediate character of f eis
an Fy hybrid. At left, Nicotiana panicu- OTaNnge (Citrus trifoliata).
Jala; in center, hybrid; at right, Nicotiana Among the seedlings ob-

dlala, :
tained, several have proven

valuable. They form a new class of citrus fruits and have
been called Citranges. Three of these varieties have been
named the Rusk, the Willits, and the Morton. The Rusk,
which is a hybrid of orange crossed by ¢rifoliala, is a small
fruit with a bitter tang like the pomelo. It makes excellent
marmalade and preserves. The Willits, coming from a

A pplication of Biological Principles to Plant Breeding 129

cross of orange upon /rifoliata, is a rough, but thin-skinned
fruit, resembling an orange in appearance but a lemon in
flavor. It is used as a condiment or for citrangeade. The
Morton, coming from the same kind of cross as the Willits,
is a large, juicy, almost seedless fruit, only slightly more
bitter than the sweet orange.

Young trees of these three varieties have endured a
temperature of eight degrees above zero, and it is thought
that by the use of them and of similarly obtained varieties,
citrus fruit culture can be extended fully 400 miles north
of the present region.

In connection with this description of the production of
new citrus fruits it may be well to mention that they are
sometimes seedless. In fact, seedless fruits are often
obtained by crossing. In true annuals reproducing by seed
only, such productions would be of no value, for they would
perish at the end of the first season. Seedless perennials,
however, are among the most valuable horticultural varie-
ties simply because they can be propagated asexually.
In floral novelties, moreover, not only seedlessness but
entire sterility is not a drawback to commercial worth,
because sterile plants are often famous for their profuse
flower clusters.

It was stated earlier that one phenomenon of hybridi-
zation was the production of fixed or constant first genera-
tion hybrids. This statement was made from hearsay
evidence. There are several cases in which either new
characters or blended characters that breed true appear
to have been formed, but they have not been studied with
sufficient care for their mode of inheritance to have been
accurately and finally decided. In crosses between cer-
tain true species, hybrids have been produced that are

130 Heredity and Eugenics

seemingly very constant and uniform. Perhaps the most
famous of these are the blackberry-raspberry hybrids first
produced by the late E. S. Carman and later by Luther
Burbank and others. Several hybrids having a commer-
cial value have been made in this genus (Rubus), and the
small number of second generation progeny that have been
grown are said to have bred approximately true. Prac-
tically, it makes little difference about the exactness of this
statement. One can simply say that for all ordinary intents
and purposes, such hybrids breed true. To the scientist
it makes a great deal of difference whether these hybrids
are definite exceptions to the law of Mendel or not. The
few data that we have are not sufficient to clear up this
point, but several hypothetical explanations of the phe-
nomena can be given that are in harmony with a belief in
the universality of Mendelianism.

Nothing is really known about segregation in these
hybrids because the variations that occur are difficult to
describe and because the plants have never been grown in
large quantities. It is likely that numerous separately
heritable characters are concerned in such crosses between
true species, and when # pairs of character are concerned
it takes four to the mth power seedlings to run an even
chance that there will be one plant like each of the parents.
When one considers that with ten pairs of characters, this
means Over 1,000,000 individuals, he can see what enormous
numbers are needed to give valid conclusions. Moreover,
these hybrids are only partially fertile and some considera-
tion must be given the possibility that selective fertilization
among the gametes of the hybrid may occur. To take a
hypothetical case, suppose two plants are crossed in which
the flowers of one are twice the length of the flowers of the

Application of Biological Principles to Plant Breeding 131

other and that the extra length of the longer flower is con-
trolled by three or four separately heritable factors. If
only a few of the egg cells and pollen cells can fuse on
account of the dissimilarity of their gametic constitution,
one would expect only those seeds to be formed that would
result from the fusion of the germ cells nearest alike.
Intermediates would therefore be more likely to occur than
extremes.

There is one other possible way of accounting for con-
stant intermediate races. In crossing species of the genus
Nicotiana, I have had plants develop from carefully
guarded and supposedly hybrid seed that were exactly like
the maternal plant. These seeds must have resulted from
apogamy or polyembryony, that is, from the development
of an immature egg cell without fertilization. The phe-
nomenon was evidently induced by the extraordinary
irritation of the foreign pollen. The question then arises:
May not the difficulty of maturing sex cells in the F, genera-
tion of a wide cross sometimes cause apogamous seed
development and therefore a continued propagation of a
constant and uniform race ?

These pieces of work illustrate the various distinct types
in the improvement of plants by hybridization.

Intentionally, little has been said regarding the fixation
of desired character combinations when the new varieties
obtained are to be reproduced by seed. The reason for this
omission is that the selective method used after hybridiza-
tion is the same as that used upon crops whose small seeds
and tendency to vary makes it difficult or unnecessary to
produce artificial hybrids. The method is Vilmorin’s and is
based upon the fact that one cannot tell the most productive
or otherwise desirable plant by inspection. The true basis

129 Heredity and Eugenics

of selection must be the average condition of the progeny
of a plant determined by actual field tests. The entire
object of selection is accomplished when a homozygous
strain or strain genotypical for the desired qualities is
isolated. The idea is simple; to put the idea into practice
successfully is often a tedious and difficult task.

As in hybridization, the ease with which results can be
obtained by selection depends largely upon flower structure.
In selection, however, the relative facility with which
artificial cross-pollination can be accomplished is of small
importance. What one wishes to know is whether cross-
pollination or self-pollination takes place naturally.

Practically all plants are occasionally cross-fertilized
naturally, and many of them have devices whereby they
are nearly always crossed; but, as we have already seen,
though cross-fertilization is an advantage to a plant, it is
not at all essential. Wheat, for example, is almost always
self-fertilized; yet it has kept its vigor for thousands of
years. The importance of this fact to the selectionist is
readily seen. If seed from several varieties of wheat is
mixed and planted, each variety remains true to its type
because of self-pollination, and each strain can be recovered
in one generation. In like manner, if desirable variations
occur in a wheat variety, it is a simple process to sepa-
rate them from the parent strain, for the two are mixed
mechanically. It is only necessary to save seed from
individual plants and grow them in separate rows or plots.
One can see immediately whether the desirable variation
is inherited or not, and if so the thing is done.

In a cross-pollinated plant the method is the same, but
the work is not so easy. The pollen is carried through long
distances by the wind or by insects, and even with carefully

Application of Biological Principles to Plant Breeding 133

isolated plots the plants are often intercrossed. Each prize
plant selected for future breeding will have had a few and
possibly many of its ovules fertilized by pollen from less
desirable strains. When these seeds are grown they of
course again fertilize the ovules of the desirable plants with
a frequency proportionate to their number. In certain
plants the process may be shortened by having recourse
to artificial self-pollination. But unfortunately this cannot
always be done. Suppose one were dealing with red clover
where the flowers are small, almost sterile with their own
pollen and produce only one seed. Im such a crop a long
and tedious method of continuous selection must be used
for there is no other way. One must simply keep in mind
the supporting principle of all selection work, that the
seeds of single plants are grown in isolated plots and the
character of the mother plant is judged by the characters
of the progeny.

We have already seen from Mendelianism and the geno-
type conception of heredity why this method is the only
proper one, but perhaps an illustration will show the
matter more clearly. The older method of selection, called
variously the German or ‘‘mass selection” method by plant
breeders and the “performance record”? method by stock-
breeders, is based entirely upon the appearance or general
character of the mother. For example, the German sugar
beet raisers have for years analyzed large numbers of
sugar beets and have grown their seed from the mother
beets showing the highest percentage of sugar. No par-
ticular attention was paid to planting from “blood lines”
of high sugar content; those beets were bred from which
appeared to be the best by their performance record in the
polariscope test. A great many of these selected mothers

134 Heredity and Eugenics

were simply high extremes belonging to “blood lines”’ that
were low in their average sugar content. These individuals
crossed with those from better ‘‘blood lines” and progress
was made very slow indeed.

In this short discussion on selection the writer has
endeavored to make clear two points that may be sum-
marized as follows. Plants are exceedingly variable but
the majority of these variations are simply accelerations
or retardations of the development of the whole or of cer-
tain parts of the plant due to good or bad environment at
critical stages of the plant’s growth. These variations are
not inherited because the reproductive or germ cells are not
affected. Other variations, however, are being constantly
produced by nature—though much more rarely—which
do effect the reproductive cells and are transmitted to the
plant’s progeny. These variations are the basis of selec-
tion. They are constant from the beginning—although
their possible presence in a heterozygous condition may
make it seem otherwise—and remain so unless changed by
a second variation affecting the same constituent in the
reproductive cells that is due to develop the character in
question. The second point to be emphasized is that the
whole aim and action of selection is to detect the desired
heritable variants among the useful commercial plants
and through them to isolate a race with the desired char-
acters. When such a homozygous race is produced, selec-
tion can then do nothing until nature steps in and produces
another desirable variation. The progeny test is the way
to accomplish this end. It does this by showing us to which
strains each mother plant belongs. It is a sure test whether
the heterozygous condition is simple or complex. If it is a
question of which seeds of a maize ear are homozygous and

A pplication of Biological Principles to Plant Breeding 145

which are heterozygous for starchiness the matter is cleared
up at once. If it is a question of which of a lot of beans is
homozygous for the gene-complex of large size, the com-
plexity of factors concerned may require a greater number
of progeny, but the test is valid in the end.

There remains for mention a phenomenon of some inter-
est even though it has produced few varieties of plants of
commercial importance. This is the sudden appearance
of a branch with characteristics different from the mother
plant upon which it is borne that may be cut off and propa-
gated asexually. It is the so-called bud sport. It is of
practically no importance outside of the production of floral
novelties. Perhaps this is accounted for by the fact that
bud variations nearly always affect the same characters
that have previously been changed in the same way through
seed variations. Furthermore, the change is practically
always the loss of a character which leaves little oppor-
tunity for the production of the real novelties through
progressive variations (Fig. 56).

The production of the smooth-skinned peach, the nec-
tarine, as a sport, from the ordinary peach tree, is the classi-
cal example of this type of variation. This is undoubtedly
simply the loss of the Mendelian factor for presence of the
down upon the fruit, and might be expected to come about
through some abnormal cell division in much the same man-
ner that variations occur in the reproductive cells. They
are usually not inherited through the seeds. This is what
would be expected. It is said, however, that sometimes
such variations come perfectly true to seed. If this is so,
one must suppose that the varying plant cell was one which
could give rise to the reproductive cells. Since nothing
definite is known of this matter, however, speculation does

136 Heredity and Eugenics

not seem wise. It is simply mentioned as one other way in
which new plant varieties originate.
In conclusion I wish to anticipate a possible question.

ic. 56.—Frond of Boston fern and types that have arisen through bud
varlation.

What help have the new biological principles been to the
commercial plant breeder? A prominent horticulturist
has said that the new discoveries have made necessary no
changes in method. With the exception that they have

A pplication of Biological Principles to Plant Breeding 137

shown the scientific basis for Vilmorin’s method of selection,
which before was not in general use, the statement is largely
true. Yet they have been of inestimable practical value.
They are time savers. In hybridization, one no longer
grows large quantities of first generation hybrids and small
quantities of second generation hybrids, for he knows that
it is in the second generation that the desirable recom-
binations of characters will occur. In many cases he can
even predict with some accuracy the exact number of second
generation individuals which it will be necessary for him
to grow to obtain the desired result. And even when this
cannot be done he knows that the blended characters of
the first hybrid generation do not mean that he has failed
to attain his object. It is simply a matter of growing large
numbers in the second hybrid generation that insures
success. Furthermore, the plant breeder has a means at
hand to show what characters are heterozygous and there-
fore unfixable. He therefore no longer wastes time in
striving for a pure strain of a heterozygous type such as the
Blue Andalusian fowl. Nor does he still regard the appear-
ance of “rogue” plants in his nursery beds as a necessary
affliction of Providence. He has learned that they are
simply recessive segregates and can be prevented by prop-
erly protected hand-pollinations.

In the field of selection the new ideas are still more
economical of time. To the belief that faith and continu-
ous selection toward an ideal would produce any desired
result has succeeded the idea that nature alone produces
variations and that man’s duty is to be alert to grasp their
possibilities and to make the most of them. No longer is
it believed that many generations of work are necessary
to purify a commercial variety of plants from undesirable

138 Heredity and Eugenics

characters. No longer is there belief that the results of
selection are continuous, that it gradually perfects a char-
acter. We work for strains homozygous for characters
that we know are there, and, by our direct methods we get
them without loss of time.

WILLIAM LAWRENCE TOWER
Associate Professor of Zodlogy, the University of Chicago

CHAPTER VII

RECENT ADVANCES AND THE PRESENT STATE OF
KNOWLEDGE CONCERNING THE MODIFICATION OF
THE GERMINAL CONSTITUTION OF ORGANISMS BY
EXPERIMENTAL PROCESSES

INTRODUCTION

Through inheritance there comes the rhythmic repeti-
tion in each specific organic form of a precise and definitely
repeated series of events ending in the production of an
individual which in time sets free from itself a highly organ-
ized and specific mass—a gamete, which, when properly
combined with some other gamete and nurtured, repeats
again the series of events which took place in the parent
bodies which preceded them. Throughout all of this com-
plex, rhythmic process a material basis, the germ plasm,
keeps intact from parent to progeny genetic lines of descent.
This continuity of material basis—first clearly recognized
by Gustav Jaeger, and later woven by Weismann into his
germ-plasm theories—while known in its gross appear-
ance and many of its behaviors, is nevertheless quite
unknown as regards its real constitution and the means
through which it does reproduce so accurately in each
generation the sequence of events characteristic of its
specific organic form.

The purely a-priori hypotheses of the “constitution”
of this substance in reality help us little or not at all as a
basis for experimental investigation. The id-determinant-
biophore fabric of Weismann, Naegeli’s micellae chains,

141

142 Heredity and Eugenics

DeVries’ pangene complex are no better and perhaps no
worse than the hypothesis that racial memory is the basis
of inheritance, or that the complex or harmonious equi-
potential systems of Driesch “explain” the phenomena.

As far as the facts of development and heredity are
concerned, they might go on indefinitely repeating any
given series of events, but there would be only. one type of
organism, alike at any and all points in the genetic chain.
Adequate evidence that there have been changes in this
series of events in the past and that changes are now going
on is found in the array of specific organic forms that exist
and have existed through geological history. How have
these changes been produced ?

The nineteenth-century biology formulated its hypothe-
ses around two widely different concepts; an extreme
transmission hypothesis in which modifications arising in
peripheral parts—soma, i.e., personal peculiarities developed
in life—are transmitted to the progeny, through being in
some manner incorporated into the germinal constitution of
the race; and the hypothesis that changes in the race arise
primarily in the germinal substance itself and appear later
in the soma.

The idea of the peripheral origin of variations through
the stress of the conditions of life dates back to Buffon,
Erasmus Darwin, and Lamarck, whose ignorance of things
now common knowledge had led them to express the opinion,
backed by much circumstantial evidence, that the condi-
tions of life, especially when changed, produced variations
which were heritable in the race. Darwin advanced the
hypothesis of an atomistic mechanism whereby this trans-
mission could conceivably be produced and upon this pro-
visional hypothesis of Pangenesis have been based _ all

Modification of Germinal Constitution of Organisms 143

subsequent hypotheses of the peripheral origin of modifi-
cations and of their inheritance.

The hypothesis of the peripheral origin and transmission
of variations is shown in diagram in Fig. 57A, where the
cause of variation (x) impinges upon the organism and

External cause of somatic
modification

pate Development Adult

PARENTS PROGENY

Fic. 57.—(A), Diagram to represent Darwin’s Provisional Hypothesis of
Pangenesis and current neo-Lamarckian conceptions and (B), the continuity of
the Germ Plasm Hypothesis of Weismann.

induces a change, variation (y), and from the cells composing
this modified part, as from all other cells of the body,
gemmules, minute masses of matter, electrolites, or some-
thing, are thrown off and these units conserve the power of
reproducing the replica of the part from which they come,
either normal or modified. These gemmules are supposed to
be gathered in the gametes, and in reproduction are supposed

144 Heredity and Eugenics

to be redistributed peripherally and to reproduce the dupli-
cate of the particular character from which they arose.
If now (x) impinging upon the organism, gives (y) a new
variation, then new sorts of gemmules are supposed to be
formed, and these on being gathered up and carried along in
reproduction by the gametes will cause to reappear in the
progeny the modified character. Repeated impact of (x)
may, in the opinion of the adherents of the view, succes-
sively increase (y). All theories of the peripheral origin
and inheritance of variations are patterned after Darwin’s
hypothesis, and although they have different expressions or
terms for the carriers of the variation: nerve force, force,
ions, electrolites, energy, etc., they are in essence the same
conception and are all operated by the same mechanism.

Radically opposed to this theory of the peripheral origin
of variation is that of the central or germinal origin of varia-
tion, in which the cause («) acts upon the germ and pro-
duces the change in the germinal constitution which, when
the germ undergoes development, produces the divergent
character (y), the variation (Fig. 57B).

Much logic has been expended upon this problem of
transmission. Weismann has made a masterly analysis
of the situation and can discover no reason for any con-
clusion other than in favor of the germinal or central origin
of all variations that are efficient in evolution. Spencer,
Cope, Eimer, Semon, Rignano, and others have tried to
equal Weismann’s logical analysis of the problem, but
without any conspicuous success. The problem is one for
experiment and not for solution by logic.

Very tiresome are the multitude of arguments, and the
arrays of “plausible instances,” and of the “facts” which
“can only be explained” thus and so. Many times has the

Modification of Germinal Constitution of Organisms — 145

whole field been gone over and summarized, and yet one sees
no progress, nor can progress be expected from this method
of attack. Only precise experimental procedure can in any
way aid in the solution of the problem, and all too often the
experiments to test these theories, especially the earlier ones,
admit of diverse interpretations, so that they are in the main
inconclusive.

In this chapter are presented some of the data accumu-
lated in recent efforts to gain precise experimental knowl-
edge of how germinal changes are brought about. I shall,
therefore, present in two divisions the data and conclusions
bearing upon the two supposed methods of change, with
such brief discussion and correlation of the already over-
discussed and over-correlated literature as may be necessary.

THE TRANSMISSION OF SOMATIC VARIATIONS

It has been proved that variations do arise primarily in
the germinal substance, and appear secondarily in the soma;
but can it be proved that modifications arising in the
soma, are transmitted to and incorporated into the germinal
constitution and appear in subsequent generations? It is
apparent that properly planned and conducted experiments
are alone of service in the attempt to solve this question.

It in no wise strengthens the position of the supporters
of the theory of the peripheral origin of variations to present
an extensive array of examples not explicable excepting
through the use of this idea, and even though it “does
explain” and ‘‘may explain” a huge array, or even all of the
problems of evolution, it does not thereby become a proven
truth. Special creation equally well explains all the
phenomena, if certain assumptions be accepted as true.
However, not until this or any other form of transmis-

140 Heredity and Eugenics

sion can be obtained in properly guarded experiments and
reproduced at will, can the process be admitted as a true
evolutionary process.

The problem, therefore, is to produce “‘somatic variations”
ina soma at such a time, or in such a fashion, that the germ
cells will not be affected by the action of the incident forces
used, and then by breeding discover if the change appears in
the progeny arising from the unstimulated germs. Evi-
dence of somatic influence upon germinal material may also
be obtained by transplanting germ glands, especially ovaries,
into different somas, as has been done by several experi-
menters.*

The recent experiments of Guthrie,’ Castle,’ and Daven-
port? are well adapted to showing any possible action of the
soma upon the germ. In Guthrie’s experiments proper
care was apparently not taken to determine the character
of the stocks used and to preclude the possibility of regener-
ated ovaries. Therefore his results are not conclusive.
Guthrie describes his experiments in the ingrafting of ovaries
between young females of single-combed black and single-
combed white leghorns, as follows:

During the summer of 1904 I exchanged the ovaries between two
black and two white leghorn pullets, weighing about 650 gms. each.
One black and one white pullet were saved for controls. All did well
for some time after the operations, but during the winter, before the
laying season began, their condition became extremely poor, owing
largely to being kept in inappropriate quarters.

‘Castle has recently given a comprehensive résumé of the ingrafting of germ
glands to which reference should be made for more detailed consideration. W. E.
Castle and J. C. Phillips, On Germinal Transplantation in Verlebrates, Carnegie
Institution of Washington, No. 144, 1911.

2>C. G. Guthrie, “Further Results of Transplantation of Ovaries in Chickens,”
Jour. Exp. Zool., V (1908).

3 [bid., 1911.

4C. B. Davenport, Proc. Soc. Exp. Biol. and Med., VIL (1910), 168.

Modification of Germinal Constitution of Organisms 147

On August 25, 1906, another series of pullets of the same strains
were similarly operated upon, controls being saved as before. They
weighed about 750 gms. each, the white ones being slightly the heavier.
All did well after the operation. No marked differences in egg produc-
tion were found between the control and operated hens, nor in the
fertility of the eggs. The operated hens at the beginning of the laying
season were somewhat lighter than the controls. In other respects
no differences were observed in either the hens, eggs, or chicks.

The eggs became fertile in two to four days after mating and on
cessation of mating the eggs became infertile in eleven to nineteen
days, the majority becoming so on the fifteenth day. Control hens
B, and W,) mated to the rooster of the same breed gave uniformly
black fetuses and chicks in the case of the black hen, and white fetuses
and chicks in the case of the white hen.

The normal black chicks had grayish-yellow breasts and throats
and frequently the under surface of the tops of the wings was light
colored as well, but the plumage of the entire dorsal surface was always
solid black. The light-colored areas on the ventral surface were
uniformly black after the first moult. Occasionally a normal black
may retain one or several white feathers in the tip of the wing per-
manently, but this is of rare occurrence and such white feathers have
not been observed in any other situation.

The normal white chicks were pure white to light buff when hatched,
but after the first moult they were always pure white. The black
hen (B,), carrying an ovary from a white hen (W.) mated to the white
rooster, gave about equal numbers of white and spotted fetuses and
chicks. (In all cases of very small white fetuses, spots may have been
overlooked.)

The white hen (W.), carrying an ovary from a black hen (B,)
mated to the white rooster, gave white, black, and spotted fetuses and
chicks. The spotted ones outnumbered the others combined.

The black hen (B.), carrying an ovary from a white hen (W.) mated
to the black rooster, gave ordinary black, and black fetuses and chicks
with white legs, in about equal numbers. In regard to the chicks from
this hen described as ordinary black, some doubt exists as to whether
the ventral light-colored area described for normal black chicks was
not lighter and greater in extent in all cases than in the normal chicks,

148 Heredity and Eugenics

The white hen (W.), carrying an ovary from a black hen (B,)
mated to the black rooster, gave uniformly spotted chicks, i.e., white
chicks, with black spots on the dorsal surface of the head, neck, wings,
back, or on the tail.

Owing to the uniform results from the controls, it may be assumed
that the strains of chickens used breed true to color. Therefore any
variations in the offspring of the operated hens were due to other
influences.

The fact that in all cases of the operated hens, white or black or
spotted fetuses or chicks were produced (i.e., the offspring showed
variations from the normal in color markings) shows:

1. That the eggs from each of the operated hens were from the
transplanted ovary. Take hens B, and W2. These hens were bred to
the roosters of their color. Had some portion of their own ovary not
been removed at the time of the operation (a remote possibility) and
was functioning, then we would have expected solid offspring like the
controls. But such was not the case. In the offspring from B, in
which the male and foster mother were black, black predominated but
white occurred. This must have come through the white ovary. In
the offspring of W2, in which the male and foster mother were white,
white was the predominating color but black occurred. The black
therefore must have come from the black ovary.

If we accept the statement that in ordinary crossing of black and
white breeds the white is dominant, then we assume that the same is
not true for this kind of (female) crossing, or that the original color
influence was more strongly preserved in the black than in the white
ovary. From the constancy in the results in the above two hens, we
may conclude that the ovaries transplanted into the other two hens,
B, and W,, were the ones functioning during the laying season also.

2. The foster mother exerted an influence on the color of the
offspring. Take hens B, and W;. These hens were bred to the rooster
of the opposite color, i.e., the color of the transplanted ovary. Yet in
the former the majority, and in the latter all of the offspring were
spotted, i.e., white with black spots on the dorsal surfaces. In B, the
male and ovary were white and the foster mother black; in W,
the male and ovary were black and the foster mother white. In both
cases white predominated in the offspring. It would seem, therefore,

Modification of Germinal Constitution of Organisms 149

if we leave the question of dominance out of account, that the foster
influence of the white hen was stronger than that of the black hen. _ If,
on the other hand, we consider the foster influence equal in both cases,
then we can explain the results as due to the dominance of the white
in the male or ovary.

Guthrie’s contention is that the ovaries were wholly
removed, and did not regenerate; that the ingrafted ovaries
developed, functioned, and were influenced by the foster
soma to produce changes in gametic constitution. The
doubtful points are concerning the nature of the stock
and its gametic make-up, which was not tested in adequate
manner, and the gametic constitution of all fowls is known to
be very complex (cf. Bateson, Saunders, Davenport, and
others); and the possibility of regenerated ovaries. Daven-
port has repeated the experiments on other but well-known
stocks, and summarizes his findings as follows:

To test these experiments [Guthrie’s] I transplanted ovaries from a
cinnamon-colored, heavy-boot, pea-combed, low-nostriled hen which
breeds true to a white, non-boot, V-combed, five-toed, high-nostriled
hen, and mated her with a cock whose characters resembled those of
the hen from which the eggs had been borrowed. Had the engrafted
ovary been functional, the chicks must have all been like the cock.
Actually, they were exactly what expectation calls for when such a
cock is mated to such a hen like the so-called foster mother. The
engrafted eggs are not functional; the ovary had degenerated.

Six experiments of this sort were made altogether and in no case
was there evidence of a functional graft; far less of an influence on the
eggs of the foster mother’s soma.

These experiments, made on better-known stock, with
many sources of error constantly in mind, give exactly con-
tradictory results. Equally convincing and identical in
result are the investigations of Castle in guinea-pigs, where
no effect of the foster soma upon the ingrafted ovary was

150 Heredity and Eugenics

found. Castle has made extensive transplantations of
ovaries, especially in guinea-pigs, and finds that:

Out of seventy-four cases six died as the immediate result of the
operation; four of these were cases in which a ventral incision was tried.

Summarizing the results of his operations he finds that in

the results of the entire series only one grafted animal had young
from her grafted tissue; grafted ovaries functioned in six other cases,
but did not produce young. Ten animals regenerated their own ovaries,
and three of these had young. Forty-two showed post-mortem com-
plete atrophy of the genital tract and absence of ovarian tissue. The
remainder comprises fifteen cases in which results were not fully deter-
mined.

On January 6, 1909, the left ovary was removed from an albino
guinea-pig (Fig. 58B), then about 5 months old, and the ovary of a pure
black guinea-pig about a month old (Fig. 584) was fastened near the
tip of the uterine horn, distant a centimeter or more from the site of the
ovary removed. One week later, January 13, a second operation was
performed, in which the right ovary of the albino was removed, and as
a graft was introduced the ovary of a second young black guinea-pig
of like age with the first but of different ancestry. After the albino
had fully recovered from the second operation she was placed with an
albino male (Fig. 58C), with which she remained until her death about
a year later.

On the 23d of July, 198 days after the first operation, she gave
birth to two female young. One was black, but bore a few red hairs.
A photograph of this animal at the age of two or three months is shown
in Fig. 58D. The other young one was likewise black, but had some
red upon it, and its right forefoot was white (Fig. 58£).

On October 15 the grafted albino bore a third young one, a male,
which, like those previously born, had a few red hairs interspersed with
black. A photograph of this animal is shown in Fig. 58P.

On January 11, 1910, the grafted albino was observed to be pregnant
for the third time, and this time she was very large. Unfortunately,
on February 2, she died of pneumonia with three full-grown male
young im utero. The skins of these animals were saved and a photo-
graph of them is shown in Fig. 58G, H, and A. Like the other three

Modification of Germinal Constitution of Organisms — 151

YOUNG 10] PURE BLACK LINE AND SOURCE
OF TRANSPLANTED OVARIES IN g No 27

QUNE SO LINE

ALBINO

ALBINO

Cc

9 27 crossep 6654 AND
REMAINED TOGETHER
UNTIL DEATH OF 9

3 No.654

K

DIED AND THEIR BLACK COAT-
ED FOETUSES WERE REMOVED
FROM HER UTERUS
Fic. 58.—To show the lack of effect of foster soma upon introduced ova
(Modified from Castle.) See text for further discussion of this figure.

152 Heredity and Eugenics

young they were black, but with a few red hairs among the black ones.
They bore no white hairs.

An autopsy made an hour after the death of the mother showed on
the left side a distinct ovarian mass about a centimeter from the coiled
part of the oviduct; that is, approximately the position where the
graft from the pure black guinea-pig was fastened at the first operation.
On the right side the mesentery of the oviduct was adherent to the
body wall where an incision had been made at the second operation,
and a small amount of tissue, regarded as possibly ovarian, was there
observed. ‘The tissue from the left side was found to contain numerous
large egg follicles, some already well advanced, containing a lymph space;
in addition a number of corpora lutea were observed. On the right
was found a small amount of undoubted ovarian tissue, with one
well-advanced egg follicle, but the whole apparently was strongly
encapsuated, so that no eggs could be discharged even if they came to
maturity.

It is interesting to note that both grafts persisted, though taken
from different animals and transferred at different times. This result
suggests a possible susceptibility on the part of the animal grafted.

Female 1,970, a daughter of the grafted albino, was mated with
the albino male, her father, and bore three young, two of which were
albinos and one black with some red hairs. If female 1,970 had been
the daughter of a pure black mother, instead of a grafted albino, we
should have expected her to produce an equality of black and albino
young. The observed result was the nearest possible numerical
agreement with this expectation.

A control mating of the albino male was made with a female of pure
black stock. As a result there were produced two litters of young,
including five individuals, all black, but with red hairs interspersed.
This result shows that the red hairs found on the six young of the
grafted albino, were due, not to foster-mother influence of the grafted
albino, but to influence of the male parent. The young of the
grafted mother were exactly in color such as the black guinea-pig which
furnished the graft herself might have been expected to bear had she
been mated with male 654 instead of being sacrificed to furnish the
graft. The white foot borne by one of the young forms no exception
to this statement. Spotting characterized the race of guinea-pigs from

Modification of Germinal Constitution of Organisms 153

which the father came. He himself was born in a litter which con-
tained spotted young, whereas neither the pure-bred black race that
furnished the graft, nor the albino race that received it was character-
ized by spotting.

Inasmuch as the offspring of albino parents are invariably albinos,
it is certain that the six pigmented offspring of the grafted female were
all derived from ova furnished by the introduced ovarian tissue taken
from a black guinea-pig. This tissue was introduced while the con-
tained ova were still immature, and it persisted in its new environ-
ment for nearly a year before the eggs were liberated which produced
the last litter of three young. These young, like the earlier litters,
gave no indication of foster-mother influence in their coloration.

The conclusion is forced upon us that the egg cell during its growth
does not change in germinal constitution. Its growth is like the
growth of a parasite or of a wholly independent organism; what it
takes up serves as food; this is not incorporated merely in the growing
organism; it is made over into the same kind of living substance as
composes the assimilating organism.

In all of these transplanted germ glands, it is true, as
Castle recognizes, that his evidence and that of others does
not disprove the possibility of foster-soma influence, but it
is certain that the evidence is at present entirely against
such influence. There are, however, two possibilities present
in these experiments which should be kept clearly in view:

1. The transmission of some character from the foster
soma to the germ and its incorporation therein.

2. The power of the foster soma to produce new surround-
ings as a result of the transplantation, thereby arousing
new physical or chemical activities incident upon the trans-
planted germ cells.

If the first effect occurs as a result of the transplantation,
it is to be expected and must be proven that some essentially
entire characters are introduced from the foster soma into
the alien germ cell and this seems in all critical experiments

154 Heredity and Eugenics

(Castle’s, Davenport’s) not to have taken place. As for
Guthrie’s experiments with poultry, it seems as if Daven-
port’s adequately controlled and carefully repeated experi-
ments gave results which show very clearly that Guthrie’s
cases are due to regenerated germ glands and impure stocks,
and not to foster-soma influence. The second possibility,
however, is a far different one and would show only varia-
tions of gametic constitution of the alien germs and not intro-
duced characters. In other words, there is this fundamental
difference between the two possibilities: the foster soma
may act merely as a new environmental complex providing
new physical and chemical states which may modify the
physiological activities of the ingrafted germ cells; and this
is very different from the conception of the foster soma
as formulating ‘‘a something” bearer of its characters or
character, which ‘‘something”’ it transmits to the germ,
which ‘‘something” then reproduces in development the
replica of the somatic part or character from which it
came.

Neo-Lamarckians reply to the results obtained from
these grafting experiments by the statement that the trans-
planting of ovaries is highly abnormal and would not occur in
nature, and would not be repeated in sequences long enough
to get the kinetic effect necessary to induce germinal change,
and therefore the experiments in no wise satisfy the require-
ments of their hypothesis.

The idea of repeated impacts producing an accumulated
kinetic effect only after long periods of activity finds most
complete expression in the curious theories of Rignano,’
which, however, are only another logical subterfuge to

EB. Rignano, Sur la transmissibililé des caractéres aqguis. Paris, 1906. Also
§ ce)
transl., Open Court Pub. Co., 1911.

Modification of Germinal Constitution of Organisms 155

maintain the cherished dogma of the biogenetic repetition
of ontogenetic stages and inheritance through a transmission
of some kind. Adequate answer to these hypotheses would
seem to exist in the non-inheritance of modifications of nose,
ear, lips, etc., of many savage tribes, often repeated with in-
tense kinetic effects of pain and stimulation, or of the feet of
Chinese women, bandaged and modified through long series
of generations, but these to the earnest neo-Lamarckian
are mutilations and of course are not to be expected to be
inherited. Curiously enough the “idea” only ‘‘works”’
in those instances where there are no facts or evidences
available for analytical investigation.

Distinctly different from the results of grafting experi-
ments or the arguments from plausible interpretations of
past series of phylogenetic states, are the interpretations
placed upon many experimental series not properly guarded.
Thus Semon’s interpretation of the results of many experi-
mental series is justified from his point of view because so
many investigations have not been sufficiently critical in
orientation, nor in analytical procedure. Thus, for example,
the experiments of Standfuss, Fischer, Pictet, Woltereck,
Kammerer, Pshibram, Zederbauer, and others admit of
interpretations from either point of view. What is unques-
tionably shown is change in gametic constitution, permanent
and heritable, but not capable of answering the fundamental
questions involved.

That organisms may be modified by incident conditions
there is no reasonable doubt, but the question is, how? If
the discovery of the methods of change is desired, then
experiments made upon known materials under carefully
guarded conditions are necessary, and are our only means
of obtaining real knowledge of the underlying processes.

156 Heredity and Eugenics

It is obvious that progress in the solution of the problem
can be made only through experiments based upon known
materials which must meet certain rigorous requirements.
The experiments of many observers with plants and animals
show clearly that changes are produced which are inherit-
able in following generations, but do not produce accurate
data upon critical theoretical points. Thus, for example,
Sumner’s recent work on mice is entirely of this order and
gives only unreliable results. Nor can experiments give
true data upon these points unless the following conditions
are complied with:

t. A stock of known character, whose behavior, germinal
constitution, variability, etc., have been determined for a
series of generations and kept in strictest pedigreed line
cultures. The stock for experiment must be clarified and
reduced to a homogeneous condition as far as possible,
and the presence of minor strains fully determined and
eliminated.

2. It must be known what stages in the development of
the germ cells, if any, are capable of being influenced, and
how—by any force intended to be used later as a somatic
modifier. Further, the behavior in inheritance of these
germinal modifications, if any, must be known for several
generations.

3. The somatic change must be induced at a time when
the germ has been found to be not sensitive to the stimulus
employed, so that opportunity may be provided whereby
there will supposedly be accumulated in the modified soma
that something, carrying the potentiality of reproducing
the modifications which the soma has acquired and which are
believed by many to become incorporated into the growing
germ cells as part of their constitution.

Modification of Germinal Constitution of Organisms 157

4. In any experiments four parallel series must be
carried: (a) a parent stock from which at the start is derived
the experimental stock, (b) the controlled stock reared
parallel to the parent stock but under controlled conditions,
(c) the experimental stock, which is a line culture sub-
jected to conditions of experiment and continued throughout
under the conditions of experiment, but from which is
taken at intervals, and (d) the test series, which are the
progeny of modified stock returned to conditions of the
control and parent, to test the constancy or reappearance
of induced modifications.

5. All lines must be group cultures mated at random to
obviate in the fullest possible manner any traces of selective
effects; that is, to breed from pairs of selected extreme
individuals might easily lead to the selective accumulation
of germinal variations normal to the race, or the isolation
of hitherto unrecognized pure lines, and thus give rise to
false conclusions.

If these conditions are complied with in any series of
experiments, the results will be an accurate answer to the
problem—no matter whether brief or long-continued action
be necessary to bring about the inheritance—because this
may also be tested if the soma be modified at a time when the
germ is not sensitive, and if this be repeated generation after
generation the results obtained become more and more
certain in their value as evidence for one or the other side of
the controversy.

Furthermore, experimental procedure of this kind will
at once give an answer to the question of the influence of the
soma as an environment upon the germ cell. That is, by
incident conditions it is easy to modify temporarily the
physiological state of the soma and gain further knowledge

158 Heredity and Eugenics

concerning the influence of altered body states in producing

germinal variations.

It will not do to dodge the issue as to experimental
methods by the citation of experiments where these precau-
tions have not been taken and say, What matters it, the end
result is the same—a modification? True, a modification,
inheritable, has resulted in so many series of experiments
that there no longer are any doubts thereon. But that
does not and cannot answer the important theoretical
question because experiments have all too often not been
properly oriented and guarded. In this there is a direct
experimental proof of the main contention of Lamarck
and C. Darwin, that incident conditions produce permanent
modifications. Naturally, in order to be permanent, any
departure from the normal must become a part of the
germinal constitution—a process which Lamarck never
attempted to explain, and of which C. Darwin offered
only a formal explanation in his provisional hypothesis of
pangenesis.

I have attempted to obtain what I considered reliable
data upon this mooted point in the inheritance of somatic
modifications, and one example of the results obtained when
the procedure outlined has been followed may be given.

To determine whether coloration changes in the soma produced as the result
of changed environmental conditions are inherited, increased, or
dropped in successive generations.

Conditions —Temperature on the average 6° C. and relative humid-
ity 10 per cent above that in nature, with other conditions natural.
These conditions were planned to produce melanic tendencies in
variation.

A pparatus.—Shown in diagram in Fig. 59.

The experiments in this series were conducted in the years 1900 to
rgo4, and were carried through ten lineal generations. The conditions
of temperature and moisture were as follows.

159

Isms

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160 Heredity and Eugenics

TABLE I

TEMPERATURE AND Humipity CONDITIONS

10 | Maxi- | Mini- | . Devia-
7 A.M vag, 1 PM|3 PeM.| BPM ay anuan |Average|tion from
z | | Normal
Temperature dry bulb | |
awa ; | |
Sas Sr |
Diy MEMES oo cile' 19: | 22" |Si! 123 ao) 43 | 3% | ga °
In experiment 2 oS. || sn) 31 | 230| 40:| 19 | 28.4 —6
Percentage of relative | | | |
ae | |
humidity: | |
“4 |
Tn matures wages *Too | 65 | 50 | BS | "Poo | tec | 43. | 74
In experiment. ..... *too | 85 | 60 | 75 | *100 | 100 55 | 84 =I
|
* Dew.

In this series of experiments 21 per cent died in the larval stage
and 9 per cent in the pupal, while 7o per cent appeared as imagines with
the proper color modifications. Throughout the whole series the
greatest care was taken to prevent the conditions of experiment from
having any possible influence upon the germ cells in their growth periods
and during maturation and fertilization. This was accomplished by
removing the adults to normal conditions during the period of germ-
cell growth and fertilization, the fertilized eggs being returned as soon
as laid to the conditions of experiment.

ee ee
A Experiment 275, Control Experiment 27a, Subjected
Generations Kept in Normal Conditions to Conditions of apes ment
ee are 27b 27a
Dice os nae7b 27a
100 ieeereree 9270 27b yo
DV iirigh tt nee 27b 27bt 27a 270
Wage ste 276 27bt 27a 27at
Vib roca ee 270 270% 27a 27a"
Vile haces 270 : 27a? 27a 27a"
aa a
NTE asceanatas tet 270 27a? 27a 27a" 27a»
EXe a ranons 27b 27a? 27a 27a" 27a»
Meisiins 27b 2702 27a 27a 27a"

Fic. 60.—To show the different parts of an experiment, in which L
decemlineala was subjected to conditions which would modify the soma without
modifying the germ plasm. The generations underscored were subjected to the
conditions of the experiment; those not underscored were kept in natural

surroundings.

Modification of Germinal Constitution of Organisms 161

By this means the color changes induced by these experiments were
known to be purely somatic modifications. Moreover, a control series,
derived from the same parents, was kept under normal conditions as a
check. During the series also several lots were taken from the experi-
ments and placed for several generations in normal conditions, and were
then returned to experiment, and likewise lots were taken from the
control and placed in experiment; and subsequently returned to con-
trol. In this way a complete check was kept on the experiments. In
Fig. 60 are represented the generations experimented upon and the
proceedings followed with each.

The experiment was divided into two parts—the experiment proper
(27a) and the control (27)). In 27a the beetles were subjected to the
conditions of experiment during ten lineal generations, with results
shown in Fig. 61. A maximum deviation in coloration was produced
at once toward a melanic state from which there was no deviation either
above or below in the succeeding generations. In the third genera-
tion of 27a the progeny were divided into two lots of equal size, one of
which was kept in the conditions of experimentation, and the other
returned to natural conditions. This second lot, known as 27a', after
being bred during four generations in normal surroundings, was further
separated into two portions, one of which was still kept in normal con-
ditions as 27a™, while the other was returned to the conditions of
experimentation as 27a'?. When the beetles in 27a" were returned to
normal surroundings, they at once resumed their natura! characters
and did not deviate therefrom during the four generations of 27a and
the three of 27a", or seVen in all. However, the effect upon 27a"? of
being returned to the conditions of experiment was an immediate
return to the maximum melanic tendency before observed. From
the sixth generation in 27a another lot of beetles, 27a, were taken
and reared in normal conditions, with the result that they also immedi-
ately reverted to the parental condition, and the same was true of 2743
in the ninth generation. In experiment 274 there appears a slight
oscillating variability which, however, is of no consequence. In the
second generation 27) was likewise separated into two lots of equal
size, one of which, 27, was retained as control, while the other, 270",
was placed in the conditions of experimentation for four generations,
and later in the seventh generation returned to control with 270.

162 Heredity and Eugenics

The effect upon 275' was an immediate production of the maximum
melanic condition, which was retained throughout the four generations
of experimentation, and lost only when 270! was returned to control.

In Experiment 27 there was no artificial selection, all imagines being
allowed freedom to mate and breed as in nature; hence the only
selective influences present were those exercised in the mating of the
beetles and by the conditions of the experiment, which eliminated a
small percentage.

From the data of this experiment the following conclusions are
derived:

1. A deviation in an environmental complex at once causes the
polygon of somatic variation and the modal class to shift as far from
the normal as it can go under the given condition, and keeps them there
until there is a return to the normal environmental complex, when the
somatic variations also at once return to their normal state.

2. The color variations employed in experiment, which are purely
somatic, are the direct result of a response to changed environmental
conditions, in terms of increased or decreased activity in pigmentation.
They may change as rapidly, as frequently, and in as many directions
as the conditions producing them change, and they have no influence
whatsoever upon the coloration of succeeding generations.

This experiment, one of the earliest in my series, illus-
trates fairly well the results obtained in several others
carried out with the same end in view. In all, the result
has been a uniform one, and entirely against the idea of
transmission of somatic modifications. I have had many
instances when I thought at first that a somatic transmission
had taken place, but in all, further analysis and repetition
clearly showed some defect in experimentation; and in no
case have I been able to duplicate one of these occurrences,
much less obtain experimental proof of somatic transmission
in a repetition of the experiment.

It is unfortunate that so many of the published experi-
mental investigations of this subject are open to diverse

163

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ication o

Modi{

Modal class of parent generations

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104 Heredity and Eugenics

interpretation and are not elucidations of the problems.
The main reason why this is so is that the materials that
have been used and the methods of experimentation have
not been properly guarded. Thus, for example, the recent
results of Kammerer with various amphibians and Lacerta,
Woltereck’s investigations upon Daphnia, Zederbauer’s
experiments with Bursa, Sumner’s with mice, as well as all
of the older experiments, admit of ‘‘interpretation” from
either point of view. Thus Semon “interprets” all of these
and many more besides as showing the strength of the neo-
Lamarckian position at the present time. A neo-Darwinian
could make an equally good case of the same data.
At present the conclusive evidence from Castle’s trans-
plantation of ovaries in guinea-pigs, Davenport’s negative
results with poultry, and experiments like those with color
in Leptinotarsa have all given exactly the expected result
without qualifications. MacDougal, in discussing some of
these problems, says: ‘‘The time has now arrived when the
claimants for neo-Lamarckianism and all of its conclusions
must show cause for its further consideration, or else allow
it to drop from the position of being seriously taken as a
method of evolutionary advance.”

With this most biologists will at present agree, but
unfortunately, from time to time, some careless experi-
menter with more partisan enthusiasm than judgment or
experimental acumen will come forward with conclusions
derived from experiments wherein the most elementary
essentials of genetic research are ignored and reassert the
transmission of somatic changes. Present experimental
evidence, where critical, clearly indicates the increasing
doubtfulness of the validity of the hypothesis of somatic
transmission.

Modification of Germinal Constitution of Organisms — 165

THE DIRECT MODIFICATION OF THE GERM PLASM

Since there are the best of reasons for the conclusion that
there is conditioned in the germ plasm the basis which
determines the presence and manifestations of organic
characteristics which are permanent in the race and in evolu-
tion; and in that there are equally good reasons for a tena-
cious adherence to the idea that all variations which are
productive of evolutionary changes arise primarily in the
germ and appear secondarily in the soma, it follows that
any and all methods whereby changes are produced in the
germinal material are of paramount interest. Modifications
in this germinal material are the basis of permanent depar-
tures from the racial mean, and at present the methods of
production and cause of germinal variations are of great
practical interest and value as well as of theoretical impor-
tance. Germinal variations have been suggested to arise
by five main methods.

The direct action of external forces was the first to be
suggested and is generally admitted to be an effective cause
in the production of germinal variations. This was a mode
of modification suggested by Buffon and Erasmus Darwin,
later elaborated by Lamarck, and made the basis of his
theory of evolution without any consideration whatsoever
as to whether the variations were somatic or germinal. A
half-century later variations which were supposed to have
originated through the action of external conditions pro-
vided in the main the array of individual differences upon
which Darwin founded his theory of the ‘origin of species,”
by means of natural selection.

: Arising from the work of Darwin, and accentuated by the
neo-Darwinians, is the idea of the production of variations

106 Heredity and Eugenics

through selection, but how selection is conceived to pro-
duce these results depends very largely upon an endless
array of unproven neo-Darwinian assumptions.
Hybridization is known to be productive of germinal
variations, and in domesticated organisms a considerable
number of useful forms have thus arisen. Frequently,
however, these commercial hybrids, appearing to be con-
stant, are only first generation hybrids indefinitely per-
petuated by cuttings, as are many kinds of oranges, apples,
grapes, etc., and most of these, if allowed to reproduce
sexually, would in subsequent generations break up into
the component types out of which they were built. There
is evidence, however, to warrant the assumption that
hybridization does result in the development of permanent
modifications which are new to the strain in which they arise,
and which persist indefinitely. Moreover, hybridization is
a potent means of creating new and diverse combinations
of existing qualities and attributes, which may account
for no small portion of the “‘species”’ in nature, as well as in
domestication. To what extent hybridization is a source of
germinal variations in nature is undetermined, and this
condition is largely due to the persistence of the dog-
matism that hybridization is of rare occurrence, is ab-
horrent to species in nature, and is really a product of
domestication and the supposed loss of specific integrity
and chastity induced by man and cultivation. Statements
of this kind, however, are entirely a-priori orthodox preju-
dices without foundation in fact. Recent work, especially
by botanists, shows a considerable and increasing array of
hybridizations occurring in nature, for example, in violets,
which exhibit an abundance of crossings, with many resulting
hybrids. Moreover, this condition is by no means limited to

Modification of Germinal Constitution of Organisms 167

violets or plants, but is coming to be recognized as common
in nature.

The production of germinal variations occurs by combin-
ing slightly different conditions of the same attribute in the
zygote (fertilized egg). This process, amphimixis, commonly
advanced by neo-Darwinians, has at present almost no evi-
dence in support of the theory that departures beyond the
normal range of variation can be produced thereby, but it
is at least a conceivable method by which variations might
well arise, and is open to direct experimental investigation.

The origin and development of variations through the
operation of orthogenesis, a name descriptive of a condition,
but personified to represent the agencies productive of the
condition observed. It is conceivable that changes started
in one direction or another may continue in that direction
on the basis of the operation of the law of inertia, in a
uniform direction and at a uniform velocity until they reach
limits imposed by the physical nature of the part or of the
organism in which they arise, or until they reach a stage of
development where they become of selective value, and may
be accelerated, retarded, or turned in other directions.

In all of these possible modes of origin of germinal
variations two groups of factors are always involved: first,
the physical constitution of the material, with its array of
qualities, attributes, and conditions, which is always the
genetic product of an immense series of antecedent stages;
second, incident forces from without the germinal material.
These two groups of factors sustain definite and fundamental
relations to each other, and the effort to understand the
relations between these two fundamental groups has
stimulated much of the investigation of the last decade.
The physical or gametic constitution is the constant, and

168 Heredity and Eugenics

the external conditions are the variable in the complex,
and elimination or understanding of the most obvious vari-
able is the first step in the study of gametic constitution
and modification. Concretely, then, what is the réle of
external factors in the production of germinal variations ?
Satisfactory evidence as to the rdéle of external factors can
be obtained only through careful experiments. These may
be either experiments under laboratory conditions, or ex-
periments in nature, and, if possible, both should be carried
on at the same time upon the same materials.

A. The Idea of Sudden Transmutation in the Germinal
Material

Succeeding Darwin, there arose a group of followers—the
neo-Darwinians. Possessing all the attributes of followers,
unable to grasp the breadth of view of their master, and see-
ing but a particular phase of his general teachings, they
endeavored to raise that to undue prominence and make it
a universal motive force in the evolution of organisms.

The neo-Darwinians in the last quarter of the nineteenth
century, under the leadership of such men as Weismann,
created what Eimer has termed the “principle of omnipo-
tent natural selection.” It was attempted to establish pur-
poseful selection as the sole efficient cause of variation and
evolution in organisms, and in the effort, Weismann went
so far as to place the selective process, not in the outside
world, but in a microcosm within the germ plasm, making
it in every way incapable of investigation, impossible of
observation, and all-inclusive.

Few today attach much importance to Weismann’s
‘germinal selection,” and the Weismannian theory remains
in biological history one of those curious ideas comparable

Modification of Germinal Constitution of Organisms 169

to the quadrille of the centrosomes. The last of the curious
hypotheses developed by the neo-Darwinians is that weird
phrase of biology which took its rise from the work of Bates,
Miiller, and Trimen, and which has been developed into the
present theory of mimicry. Its supporters would have us
believe that much transmutation is based upon a mimetic
principle aided by the subsidiary principle of recognition
marks. Here utilitarian variation and purposeful selection
run riot and produce in every case a definite end, a pro-
tected form. Naturally, these curious and thoroughly
uncritical ideas, current among the neo-Darwinians, are
their own answer.

At present the neo-Darwinian concepts offer nothing
that is of use as a working hypothesis in the further investi-
gation of evolution, nor any logical ground for observation
and induction in nature. The neo-Darwinian situation,
and, also, the neo-Lamarckian are in reality two of those
common developments which arise in every line of human
thought—intellectual culs-de-sac.

More as a protest against the neo-Darwinian situation
than for any other reason, there arose, simultaneously, in
England, on the Continent, and in America, the modern
saltationist school. Thoroughly bored with the repetition
by the neo-Darwinians of the same old facts sung to the
same old tune, Bateson in England, DeVries on the Conti-
nent, and others, determined to find an outlet, and all, I
think, obtained their original inspiration from the recog-
nition by Darwin that in many species variations repeatedly
occur which stand apart from the rest of the population, and
frequently are prepotent when bred back to the parent
stock. Further, Darwin in his Origin of Species and The
Variations of Animals ant Plants under Domestication cites

170 Teredity and Eugenics

many instances in which there is good reason for believing
that domesticated varieties of pigeons, birds, and cattle,
and many plants, have arisen by the sporting process.

Most biologists have insisted upon retaining that
cherished dogmatism of the seventeenth and eighteenth
centuries that there must be discontinuity between species,
and the idea seemed plausible that if discontinuity existed
between species when they were finished, there was no
a-priori reason why it could not have arisen at the start.
Therefore, Bateson, in the latter part of the nineteenth
century, gathered what data existed in the literature on
sports and discontinuous variations, in the effort to find an
outlet from the cul-de-sac into which neo-Darwinianism
had led English biologists.

At about the same time DeVries in Holland became
convinced from a somewhat different point of view that a
similar process must be operative in the production of
species in nature. DeVries sought, therefore, to find in
nature plants which exhibited the kind of variation that
he conceived of as being the basis of transmutation, and
finally discovered that Oenothera Lamarckiana seemed to
be undergoing exactly the sort of process which he hoped
to find.

Others became convinced that there were possibilities
in this direction, and as a result there is at present a well-
developed school of saltationists whose central idea is
that progressive and efficient steps in transmutation take
place through sudden, steplike variations, producing, as
DeVries asserts, something quite new each time.

Directly associated with the development of this idea,
and contributing much to its development, was the redis-
covery of Mendel’s paper on the ‘Behavior of Hybrid

Modification of Germinal Constitution of Organisms 171

Peas,’ which gave impetus to investigations that strength-
ened and extended the saltationist conception.

It would be rash indeed to deny that there are “‘sports”’
in the Darwinian sense, and DeVries’ “mutations” are
asserted by some to be but the same kind of variations
with a new name, but the fact of the occurrence of sudden
variations is established beyond doubt. However, next
to nothing is known concerning the rise and behavior of
these sports and the part they play in the transmutation of
organisms in nature, and it may be wisest to suspend judg-
ment as to the relative importance of saltation as a method
ofevolution. The saltation conception, however, considered
in its broadest sense, has decided advantages over the neo-
Darwinian and neo-Lamarckian positions, because it is
directly open to experimental study and does serve as a
fairly logical and workable hypothesis for investigation. In
its broadest aspects it is in no way like Weismann’s theory,
although DeVries has endeavored to give it a position not
unlike that of germinal selection by placing all essential
processes in the hypothetical pangenes. Out of this situa-
tion perhaps the greatest advance that has been produced
is the revival of interest in bionomic investigations and the
clearing of the mist from many questions, even though the
questions have not been fully answered. Regardless of what
the future may have in store, the saltationist school has
rendered biology a very real and lasting service in arousing
new enthusiasm for the experimental study of evolution
problems and in breaking away from neo-Darwinianism,
neo-Lamarckianism, and orthogenesis, whose deadly chants
were slowly but surely lulling into complacent inactivity the
greatest heritage from Darwin—the experimental study of
evolution problems.

L72 Heredity and Eugenics

The saltationist school, aside from a considerable num-
ber of clearly formulated questions, has very clearly raised
the issue as to whether changes in the constitution of the
germinal material are accomplished by the slow quantita-
tive accumulation of useful variations, or take place by
sudden steps, appearing with discontinuity in the end result.
Much experience with this method of quantitative accumula-
tion had given adequate reason to distrust it as a particularly
potent means of inducing experimental change, and refuge
not infrequently had been sought in the soul-satisfying
myths of germinal selection, orthogenesis, isolation, growth
force, bathmic force, and many other intricately contrived
and all inclusive hypotheses, but all were found utterly
useless for actual experimental investigation and analysis,
such as is demanded in physical and chemical science.

In seeking for an outlet from the culs-de-sac of evolu-
tionary science as it existed in the last quarter of the nine-
teenth century, DeVries concluded that change, per saltiume,
was quite as lable to be a real method of transmutation and
sought to put it to a test by seeking in nature for species
of plants that were undergoing this kind of change if such
existed. Darwin had already noted the frequent occurrence
of large sudden departures in both plants and animals, but
was of the opinion that both large, sudden, and small
fluctuations were operative in transmutation phenomena.

The discovery of O. Lamarckiana (Fig. 62) in an
abandoned field near Hilversum in Holland, into which
it had escaped from a near-by park, provided most favor-
able material for DeVries’ further study. Here it grew in
quantity with two apparently newly arisen derivative forms,
O. laevifolia and O. brevistylis. Plants from this waste
land were taken into the botanic gardens of Amsterdam

Modification of Germinal Constitution of Organisms — 173

Fic. 62.—Oenothera Lamarckiana, the original type of plant used by DeVries
in his experiments. This is the stock from Hilversum, from which arose in suc-
cessive generations a series of new forms by sudden jumps. From DeVries.

174 Heredity and Eugenics

and there gave rise to several new types during the years
of DeVries’ observation. Some of these arose in the
experiments but once, as for example, O. gigas (Fig. 63),
a tall, robust form with large flower, the finest of all the new
types. It appeared in 1895 and was one out of about 14,000
plants, but was not the only new type to appear in the crop
of that year. Six others were found: O. albida, of which
there were fifteen examples (Fig. 64); O. oblonga (Fig. 65),
of which 176 specimens appeared; O. rubrinervis, eight
specimens; O. scintillans (Fig. 66), one specimen. This
year gave the greatest number of new forms of any, although
other years (1896, 1897) gave all but the O. gigas.

A good idea of the real differences existing between
these derivative forms and the parent plants is given in
Fig. 67, where the plants are shown growing side by side.

In Fig. 68 is given in condensed form the line of descent
and the appearance of the derivative forms from year to
year.

If all be granted that is claimed for the separateness of
these types, and admitting also that they are absolutely
constant in type and in heredity, there still remains one
striking difference between these DeVriesian ‘‘mutations”’
and the ‘‘sports,” ‘‘saltations,”’ etc., of other writers:
namely, the mutations occurred in numbers in every genera-
tion for a considerable period, through several consecu-
tive generations; the sports of Darwin appear but once,
rarely, and not successively. Upon the curious findings
in O. Lamarckiana, DeVries has built the hypothesis of
a premutation period in which the germ plasm was
elaborating new pangenes which, when the pangenes reached
a certain point, broke out into visible manifestation as
mutants, and he further supposed that after a time the new

Modification of Germinal Constitution of Organisms 175

Fic. 63.—Oenothera gigas, a mutant of Oenothera Lamarckiana. This form
arose but once in DeVries’ cultures (in 1895), out of a culture of 14,000 seedlings.
From it has arisen a strong race now cultivated in many gardens in Europe and
America.

170 Heredity and Eugenics

Pic. 64.—Oenothera albida. Another type which has arisen from Oenothera
Lamuarckiana, occurring with considerable frequency in successive years.

Modification of Germinal Constitution of Organisms 177

Tic. 65.—Oenothera oblonga. A type which has arisen from Ocnothera
Lamarckiana.

175 Heredity and Lugenics

Fic. 66.—Oenothera scintillans. A rather rare mutant of Oenothera Lamarck-
tana.

Modification of Germinal Constitution of Organisms 179

O. rubrin

O. Lamarckiana

illans

O. sci

O. givas

O. hirtella

O. nanella

O. Lamarckiana

Fic. 67.—A series showing Qenothera Lamarckiana and several of its mutants growing side by side, illustrating

From DeVries.

characteristic differences in height, habit, foliage, branching, and flowering of the different forms.

180 Heredity and Eugenics

pangenes would cease to be produced, or at any rate that
mutation would cease and the parent species go on as before.

Genera- : O. rubri- O. Lamarck- O. scintil-
tions O. gigas O. albida O. oblonga nervis tana O. nanella O. lata lans
Saka Ga sea Bois sSeet see cock ses eee sase ke way aeceae aguas -+-----—4
Gen. 8 j i
Too 5 1 6. hivoo-| 21. | 4
aero
1898 | 9 0 3700 11,
a fi 29 3 | 1800 9 eed
Piette Seiy ey oe Sei an ae
Gen. ! 25_| 135 | 20 | gooo| 49 |142| 6
| i

nae ee 15 {76 8 | 14000 60 | 75 | 4

1895

Gen. 3
1890-91

Gen. t
1886-87

Mutants and Number observed in O. Lamarck- Mutants and Number
different years lana observed in different years
The mu-
tating

stem form

Fic. 68.—Diagram showing in condensed form the genealogy of the Oenothera
Lamarckiana family and its various mutants during successive years. The num-
bers under each type represent the number of new types observed in each year.

As far as causes were concerned, DeVries had little to offer
except the suggestion that the cause was ultimately probably
an external one.

Modification of Germinal Constitution of Organisms 181

There is not the least doubt as to the behavior of O.
Lamarckiana and the appearance of the ‘‘mutants,” and it
appeared to many that there was a good chance of producing
“mutating races” by external forces acting upon the germ
of the parent race. The last decade has produced a deal
of evidence that external forces can produce germinal
changes, but these are in all instances immediate and final.
New, divergent types, more or less separated from the
parent, have appeared, but in none are there subsequent
mutations.

I had been at work upon this problem and had found
and reared sports of Leptinotarsa decemlineata as early as
1893, and on the appearance of DeVries’ work I began in a
systematic way to try to produce mutating races by the
use of external forces. I have thus far positively failed to
produce a mutating race by these agencies, although I have
been able to get changes in profusion, some of which I shall
describe later.

In too1 I tried to produce a mutating race by crossing
L. decemlineata, L. juncta, and L. pallida, with the idea
that perhaps the interbreeding and combination of the
chief characters of the three into a hybrid complex would
produce a type which under changed conditions of
growth and development, or of changed or adverse
environment, would give the mutation behavior of O.
Lamarckiana. The early experiments were just beginning
to show promise of interesting results when they were
brought to anend. As subsequent results have shown, this
was a good working hypothesis but these first experiments
would not have led to the results wanted. In 1902 Bateson
suggested that the mutation phenomena in Oenothera was
possibly akin to a Mendelian splitting of a hybrid type.

182 Heredity and Eugenics

From the year 1904 onward I have been able to carry
out a number of suggestive experiments in the further effort
to produce a mutating race experimentally.

EXPERIMENTS IN THE SYNTHESIS OF A MUTATING STEM RACE

An extensive set of these experiments has been in
progress for some years, some of which have now developed
far enough to allow of rather definite statements. The
method employed has been to take species derived from
nature from some restricted locality, to keep close watch
upon what goes on in this locality, and also to analyze the
composition of the species from this locality by cultures in
the laboratory. In this way, stocks of known character are
obtained from experiment, and also natural stocks whose
attributes are well known are developed in the type localities.
In the experiments in synthesis either pedigreed stocks from
the laboratory, or the stocks from nature, or both, are
placed in nature upon their food plant in isolated localities,
or in large cages, and allowed to breed as if the introduction
were a natural one.

In 1904, an isolated area of about an acre upon the
southern slope of a barranca, near Cuernavaca, was planted
with food plants, upon which both L. signaticollis and L.
undecimlineata would feed. In July, 1904, this spot was
stocked with a culture of 210 specimens of L. signaticollis,
from a standard location about a mile and a half distant,
and 354 specimens of L. undecimlineata, obtained at El Hule,
on the banks of the Rio Papaloapan. The groups were
equally divided between the sexes, were young and vigor-
ous, immediately began breeding, and intercrossed freely.
Under experimental conditions these forms cross freely in

Modification of Germinal Constitution of Organisms 183

both directions, but out of them no new characters come
as the result of ordinary crossing.

In the first generation of this colony there was an
abundance of individuals of both sexes of the signaticollis
type, and of the wndecimlineata type, and of a highly
variable intermediate hybrid type. A census was made of
the population on August 14 to 17, with the following results:

Signaticollis Type Mid-Type Undecimlineata Type
4,518 11,744 5,001

In this experiment, it was, of course, impossible to tell
from inspection whether the signaticollis individuals were
pure signaticollis, or pure signaticollis and a hybrid with the
signaticollis dominant, and the same was true with respect
to the wndecimlineata. All of the beetles entered into
hibernation during the latter part of August and early in
September, 1904. The food plants survived the long, hard,
dry season and came up in the spring of 1905 in abundance,
and in June, 1905, individuals of all three types emerged
and were found to be interbreeding freely. A census made
of the individuals which emerged late in June gave the
following results:

Signaticollis Type Mid-Type Undecimlineala Type
1,027 1,744 478
which clearly indicate that through some cause the hiber-
nating conditions of the location were favorable for signati-
collis, but decidedly unfavorable for the wundecimlineata
and for the intermediate hybrid type. These individuals
were allowed to interbreed freely and produced a numerous
progeny, in which the larvae were of four different types:
white without spots, white with spots, yellow without
spots, yellow with spots. The second generation emerged
from the middle to the end of July, 1905, and showed a

184 Heredity and Eugenics

huge preponderance of the s7graticollis type. The census
of a random sample taken the last week in July gave the
following count:
Signaticollis Type Mid-Type Undecimlincata Type
1,244 1,192 307

These individuals were not removed from the colony;
the census of the sample was made, the individuals put
back, and the colony allowed to encounter the conditions
and behavior which it would meet in a state of nature.
Nine pairs, taken at random, of the undecimlineata type
were bred out as pedigreed cultures during August and
part of September, 1905, and gave uniformly an undecim-
lineata progeny. Seven pairs of the szgnaticollis type,
which were bred out, gave uniformly a signaticollis progeny,
and out of five other pairs there appeared individuals of the
mid-type and of the wndecimlineata type, showing that
some of the signaticollis type were hybrid in character.
Six pairs of the mid-type were also bred out as pedigreed
stock, and showed themselves to be in every case hybrid.
The third generation was produced in August and early
September, t905. In this the larvae were of the same
four classes, but showed a huge preponderance of yellow
larvae (yIS). A count made late in August, when perhaps
the bulk of the larvae had entered into pupation, gave the
following results:
Whs Whs ylS Vis
205 227 S40 321

The adults of Generation III emerged early in September;
a census made about the middle of September gave the
following:

Signaticollis Type Mid-Type Undecimlineata Type
2,452 O27 218

Modification of Germinal Constitution of Organisms 185

showing again a marked decrease in the wndecimlineata
form, a lesser decrease in the intermediate hybrid type, and
a much greater relative increase in the signaticollis type.
These hibernated during the winter of 1905-6 and emerged
in June, 1906. They were allowed to interbreed freely.
The population was not seen at the time of emergence,
but in the fourth generation it was observed in July, 1906,
and the undecimlineata type and the mid-type were nearly
absent. The census made at this time, when the first
generation of the year was apparently at its height, gave the
following results:
, Signaticollis Type Mid-Type Undecimlineata Type
3,275 45 7
These then inbred and the colony was next seen in Septem-
ber at about the middle of the month, when the census of the
individuals in the colony was as follows in Generation V:
Signaticollis Type Mid-Type Undecimlineata Type
1,823 6 °
These hibernated during the winter of 1906-7 and emerged
in June, 1907, reproduced at once, and gave an abundant
progeny which emerged as Generation VI between the roth
and 25th of July. These when seriated gave the following
results:
Signaticollis Type Mid-Type Undecimlineata Type
2,255 2 °
The second generation of 1907 emerged late in August
and early in September, and of this generation the undecim-
lineata type was entirely absent, and the mid-type prac-
tically so. These hibernated and when seen in the spring
of 1908 only the signaticollis type emerged. Both genera-
tions of r908 and both generations of 1909 have developed
the presence of the signaticollis type only.

186 Heredity and Eugenics

In 1908 individuals from this location were brought to
Chicago and carried as pedigreed cultures in the labora-
tory. They have shown a complete gametic purity as far
as could be determined and none have been detected which
were hybrid in character. In this colony, isolated in its
location, through some process or other in hybridization
or perhaps by selective factors, signaticollis has completely
subjected and eliminated wndecimlineata. Inasmuch as
L. undecimlineata, when protected from crossing, lives
well at Cuernavaca, and the selective action is very low,
I am of the opinion that the swzmping of wzdecimlineata
is due to some process of hybridization. This opinion is
fully justified by experiments conducted in cages which
eliminate selective factors.

Another experiment was begun in 10905, when one
hundred individuals were taken from the standard colony
of L. signaticollis at Cuernavaca, and, with an equal num-
ber of L. undecimlineata, from El Hule, were planted upon
a vigorous growth of their food plants in a clearing made in
the Foot Hill Rain Forest, in the Paraiso district, not far
from Ojos de Agua, in the Canton of Zongolica. They were
observed to intercross freely, but there was a preponderance
of wndecimlineata-like forms, with a few intermediates,
and only small numbers of the szgvaticollis type in the first
generation. The census made of the first hybrid generation
was as follows:

Signaticollis Type Mid-Type Undecimlineala Type
° 56 1,342

A third generation was produced in late November, and
in that generation there were no sigiaticollis forms visible;
there were only a few of the hybrid intermediate type, and

Modification of Germinal Constitution of Organisms 187

these all closely approximated the wndecimlineata form
The census obtained late in November was:

Signaticollis Type Mid-Type Undecimlineala Type

(eo) Il 1,132

In 1906, 1907, and 1908 these cultures were allowed to
shift for themselves, and the food plants were nearly
swamped by the immigration into the glade of plants from
the surrounding rain forest; in fact, the whole culture was
allowed to engage in a most desperate struggle for its
existence. As far as the beetles were concerned, this was
simply a struggle for food. In 1908-9 the inroads which
had been made by other plants had so reduced the number
of Solanums that the food supply was inadequate. During
these years, however, no trace of the signaticollis type had
ever appeared. In 1908, material of the undecimlineata
type was taken from this culture to Chicago, and there
subjected to the tests of pedigree analysis, but without
any trace of the signaticollis form appearing. In both
experiments, however, at Praesidio and at Cuernavaca,
the resulting materials were different in gametic make-
up from the original species. Superficially, these stocks
could not be told from the natural species, but when used
as the basis of experiment under control conditions, it was
found that there resulted a difference in the behavior of
the subsequent hybrid generations, clearly indicating a
change in the gametic constitution of these groups of
individuals.

A series of experiments, more conclusive and under
better conditions, has been carried on, using three species:
L. decemlineata, L. oblongata, and L. multitaeniata. Of
these, in nature, L. decemlineata is limited solely to the

188 Heredity and Eugenics

United States and southern Canada; L. mutltitaeniata
entirely to the southern portion of the plateau of Mexico,
and L. oblongata to the Balsas Valley and the Oaxaca-
Guerrero Highlands. These species intercross freely under
experimental conditions and represent the following con-
trasting characters for consideration. The general ground
color of the larvae of L. decemlineata is wine red, that of
L. oblongata and L. multitaeniata chrome yellow. L. decem-
lineata and L. multitaeniata have two rows of spots
along the side in the larvae, while L. oblongata has one.
L. oblongata, as shown in Fig. 60, is long and oval in outline;
L. decemlineata, as shown in Fig. 60, is more rounded;
and L. multitaeniata is robust in type. There are also color
differences between the species, which need not concern us
here. Three experiments will serve to illustrate the pur-
pose of this paper.

In 1905, twenty L. decemlineata, from a pedigreed cul-
ture, from Chicago, twenty L. oblongata, from a pedigreed
culture at Cuernavaca, and twenty L. multitaeniata, derived
from an isolated standard locality in the valley of Mexico
south of Guadalupe, were placed on an isolated island in the
Balsas River. This island was fairly well covered with a
growth of Solanum rostratum, or a closely related form, upon
which all three species would feed. As far as could be
discovered, the island was devoid of any individuals of L.
oblongata, which occur very sparingly in that general region,
and the neighboring banks of the river and the islands were
all searched, but they afforded no trace of L. oblongata.
These introduced beetles were allowed to breed and gave
the first hybrid generation in August, 1905. In this
generation only the adults were seen and of the adults we
could recognize definitely five forms: (A) Those which on

Modification of Germinal Constitution of Organisms 189

inspection appeared to be wholly L. decemlineata; (B) those
which appeared to be wholly L. oblongata; and (C) those
which appeared to be wholly L. muiltitaeniata. There were
individuals which were manifestly intermediate hybrids, in

F

Fic. 69.—Arranged to show some of the essential differences between the
species: L. oblongata, L. multitaeniata, and L. decemlineata. (A) Showing the
form and characteristic markings of the adult of L. oblongata. (B) Adult of L.
multitaeniata, showing the more robust form and somewhat different type of
general color pattern sharply distinguishing it from both of the other species. The
elytral ground color is often dark ochre, sometimes even reddish. (C) The type
of L. decemlineata used in these experiments, somewhat intermediate between the
two other species in body form, and to a certain extent in markings. (D) Showing
the side view of a full-grown larva, with its color pattern. The ground color is
yellow and that of the adult somewhat variable. (E) Adult larva of L. mullti-
taeniala, with the characteristic color pattern. Ground color is yellow as in L.
oblongata, but darker. (F) Shows the characteristic color pattern of L. decem-
lineata; the ground color of the larvae is wine red.

form, punctation, and coloration, between L. decemlineata
and L. oblongata (D); and between L. decemlineata and L.
multitaeniata (E). Of these five forms a census was made

with the following results:

190 Heredity and Eugenics

All the individuals were allowed to remain in the colony, and
interbred freely in August, giving early in September a second
generation, of which the following census was made:

A B e D E
46 IOI go 1,292 210

These hibernated during the winter of 1905-6, and were not
seen again until September, 1906, in the fourth hybrid
generation of the culture. At this time the dominant form
was manifestly a combination between L. decemlineata,
L. oblongata, and L. muidltitaeniata, with the oblongata-
decemlincata attributes in excess of those of L. multitaeniata
(a combination between classes D and E of F, and F,):

A B C D E

7. 25 £2 2,210

The huge preponderance of this complex type, which
was neither one nor the other of the three species, suggests
at once, of course, that the results could not be due to any
selective process, because the type was not one of the
original types but a hybrid complex.

The wintering conditions of 1906-7 were especially
rigorous, at least as judged by the number of beetles that I
found in that location in 1906-7, when the following census

was made:
A B (e D E

fo) ° 4 22
This shows that during the winter practically only the
hybrid combination was able to survive. These repro-
duced and gave a progeny in July, 1907. An inspection
was made early in August, when I found only the dominant
type present in the fifth hybrid generation.

A B c D E
fe) ° fe) 1,877

The culture was not seen again until the spring of 1908,
when a considerable number of the dominant form of the

Modification of Germinal Constitution of Organisms 191

sixth hybrid generation was found emerging. These were
taken to Chicago and subjected to analytical experiments and
were found to breed true, both in group and in pedigreed cul-
tures, with this exception, that in both the pedigreed cultures
there occurred from time to time sporadic variants often
standing a considerable distance apart from the rest of the
population, which, when inbred, either with sports like
themselves, or back to the parent type, gave behaviors which
in every way are comparable to the behavior observed in
many of the forms which are supposed to have arisen by a
mutative process. These strains were kept through the
years 1908 and 1909, and gave results which strongly
suggest that the interpretation of a mutative period as
described by DeVries in O. Lamarckiana, may well be the
variability which follows complex processes of hybridization.

In 1906 operations were begun at Orizaba, and in May
the same three species from the same original stocks were
mated. Conditions at Orizaba are decidedly different from
those in the Balsas Valley. The city is 2,000 ft. higher in
altitude and the climate is very different. In the Balsas
Valley during the summer the days are bright and hot,
with even showers. At Orizaba, in the location chosen
at the foot of the Sierra Escamela, it is never above go”
even on the hottest days, and the nights are always cool,
owing to the downward draught of cool air from the moun-
tains which flows over the valley at night. The relative
humidity is high at all times, and the precipitation during
the season was 74 inches.

Under these conditions the crosses which were made
thrived as far as certain members were concerned: the
L. multitaeniata individuals were decidedly reduced by the
conditions under which they were living and the L. oblongata
individuals were hampered considerably, but to a lesser

1Q2 Heredity and Eugenics

degree. Crossing was observed, however, among the com-
ponent species in all directions, and progeny emerged in
July, showing a combination to have been formed between
L. oblongata and L. decemlineata, with the L. multitaeniata
type and attributes wanting. The population, when
examined, showed individuals which were apparently domi-
nated by L. decemlineata (A) to the exclusion (as far as
visible) of all others; individuals which were very clearly
intermediate between L. decemlineata and L. oblongata (B);
and individuals which were more or less intermediate between
L. decemlineata and L. multitaeniata (C). Of these the
intermediate between L. decemlineata and L. oblongata
existed in by far the greatest numbers, as shown by the
following proportion:

A B Cc
131 397 92

Inasmuch as this experiment was conducted in a large
cage and not in the open, it was manifestly impossible to
utilize all the individuals which emerged, so a reduction was
made for the matings for F,, excepting that any extreme
or rare types were given every advantage over the more
common types. The following materials were selected at
random from the different groups as parents of the second
generation:

A B Cc
33 36 38
32 32 32

These inbred rapidly during July and at the end of August
gave a second generation which was uniformly an inter-
mediate between L. decemlineata and L. oblongata.

B
fe) 5890

Modification of Germinal Constitution of Organisms 193

This was especially true of the adult characters. The
larval characters, however, were also variable and appeared
to be less blended into a homogeneous group.

The culture hibernated from early September, 1906,
to June, 1907. During this period a very great mortality
occurred, which was due very largely, I think, to the fact
that the culture would probably have reproduced a third
time in 1906 if it had been supplied with food and proper
conditions.

These individuals in 1907 reproduced and gave a pretty
uniform progeny of the blended type between L. decemli-
neata and L. oblongata, Generation III:

A B é

2 476 fe)
A fourth generation was obtained in tate August and early
September of the same year, which possessed the same
attributes as the third generation. In nature, this culture
was not carried beyond that stage, but material from the cul-
ture was brought to Chicago and carried through the winters
of 1907 and 1908, and the summer of 1908 and part of 1909.
It was subjected to various analytical experiments, all of
which tended to show that the type was a relatively stable
one. Individual pairs, when inbred, gave a very definite
pure line culture and groups mated at random gave the
same result; but, as in the colony in the Balsas River, there
appeared sporadic individuals, widely separated from the
parent stock, which, when inbred, behaved in every way
like DeVries’ mutants.

A culture of the same material was placed at the Desert
Botanical Laboratory of the Carnegie Institution in the
desert of southern Arizona at Tucson, near the foot of
Tumamoc Hill. In this experiment two males and two

1904 Heredity and Eugenics

females of L. decemlineata, from the typical stock at Chicago,
two males and two females of L. oblongata, and two males
and two females of L. multitaeniata were mated in the early
part of June. This culture was confined in a cage 6 ft.
square on the ground and 3 ft. high, covered with wire
eighteen meshes to the inch, thus eliminating all selection
by insectivorous enemies. S. rostratum was supplied
as food in sufficient quantity. During June and July
these reproduced abundantly and gave a large progeny
which emerged late in July and early in August. In this
first hybrid generation at Tucson there was, as in the other
cultures, a blending of the materials introduced into the
experiment, but in this culture L. decemlineata was the
dominant member of the cross, although not completely.
In the larvae six types were observed:

t. Those which on inspection appeared to be L. decem-
lineata.

2. Those which were L. oblongata.

3. Those which were L. multitaeniata.

4. Those which were intermediate between L. decem-
lineata and L. mutltitaeniata.

5. Those which were intermediate between L. decem-
lineata and L. oblongata.

6. Those intermediate between ZL. oblongata and L.
multitaeniata.

It was, of course, impossible to tell on inspection what
the constitution of each of these types was. Five classes
of adults were recognized:

A) Those which were clearly either pure, or dominants
of the L. oblongata type.

B) Those which were clearly intermediate hybrids be-
tween L. decemlineata and L. oblongata.

Modification of Germinal Constitution of Organisms 195

C) An L. decemlineata type in which L. decemlineata
was in the main dominant, but which exhibited a variable
range of variability.

D) Intermediate hybrids between L. decemlineata and
L. multitaeniata.

E) Forms which were either L. multitaeniata pure, or
heterozygotes, in which L. mudtitaeniata was completely
dominant.

Out of 1,857 adults seriated, the following census was

made:
A B G D E

47 20 Tj;3rT 261 103
This census shows that while LZ. decemlineata is either the
dominant or prepotent member of the combination, it did
not come out of the mixture entirely without contamination.
This experiment was continued in a cage exactly like
the first, and the following materials were taken at random
from the first generation as the parents of Generation IT:

A B € D E
26 26 63 38 36
29 29 62 3% 3¢

This material immediately began breeding and gave during
the month of August a large progeny which emerged early
in September, and immediately went into hibernation.
When seriated, this material gave the following results:

A B Cc D E

° 20 247 42 fo)
These passed the winter of roo8-9 in the ground and
emerged in June, 1909. All that emerged were allowed to
reproduce in the cage and were supplied with food as fast
as it was consumed. These gave a very large progeny
which appeared to be uniformly of the dominant types of the
first and second generations. Seriation of the material

196 Heredity and Eugenics

obtained from Generation III at the end of August, 1909,
gave the following results:

A B CG D E

fe) 5 362 8 °

I then mated at random for the parents of Generation
IV, one male of B, the only one that could be found alive,
three males and three females of C, two males and two
females of D, and none of E, they being absent. This
material bred at once and gave in the fourth generation a
considerable progeny, which were all of the dominant type.

Material from Generation IV, brought to Chicago in
August, 1909, placed in hibernation under experimental
conditions, and brought out to breed in the middle of the
winter, has shown that the dominant type is a fixed type,
and that it breeds true and does not split in subsequent
generations. The only splitting is that which occurs in rare
individuals in from 2 to 3 per cent of the progeny, which
stand apart from the general population as sports. These
cases are practically the reappearance of one or the other of
the component characters or combinations thereof that went
into the cross, and they do not represent in this experiment
anything in the way of characters new to the genus or family
as DeVries states to be true of his mutants, rather they
are simply the characters obtained from the different parents
from which this complex has been built up.

The same combination of material was made in Chicago
in 1908, and was run through essentially the same pro-
cedure as that of the Tucson experiment, with this difference
in the result, that at Chicago L. decemlineata completely
dominated the culture to the total exclusion, as far as analy-
sis has been able to discover, of the presence of the other
parents.

Modification of Germinal Constitution of Organisms 197

These experiments in synthesis represent what might
happen in a state of nature when species which can hybridize
migrate from one place to another and intercross. No
one realizes better than I the complexity of experiments
of this kind, the difficulties involved in the analysis of the
results, and the caution that should be exercised in making
statements from them. It seems certain from these experl-
ments, as far as they have been carried out, and they are
by no means complete, that we may definitely conclude
that when like materials are combined under different
natural environments, differences in the products, depending
upon the conditions under which the combination takes
place, result. It is certain that the type which came out of
the culture in the Balsas Valley was quite different from
that which resulted from the cultures at Orizaba, and these
are different from the dominant type which arose at Tucson.

One point of very considerable interest is the behavior of
these dominant types in exactly the way in which DeVries’
Oenothera Lamarckiana behaves, giving in each generation,
a greater or less number of rather divergent individuals,
which, when inbred, are found to be stable germinal varia-
tions.

Bateson in 1902 suggested that the mutations observed
by DeVries in Oenothera Lamarckiana are in reality due to
some sort of hybridization behavior. I am of the opinion
that Bateson’s suspicion is probably justified, at least in
some instances. I have no experience with plants, and
especially none with O. Lamarckiana, but my experience
with these synthetic experiments has suggested that the
type of behavior which DeVries has discovered, and
upon which he has built an all-inclusive theory of evo-
lution, is in reality nothing more than the reappearance

198 Heredity and Eugenics

from time to time of attributes brought into the strain by
hybridization, and which reappear in every generation, or in
frequent generations, by some process akin to Mendelian
segregation.

It seems unreasonable to advance, as has DeVries, the
idea of a premutation period, with a gradual development
of invisible pangenes, and then a final bursting of these
pangenes into a full-fledged mutation period, followed by a
gradual dying away of the mutation period which leaves
a species in a condition in which it does not produce these
sports. Rather, the explanation which Bateson suggested,
and which I have shown to be capable of creation in these
synthetic experiments, is far more plausible and more
likely to be the real explanation of the type of behavior
found.

This raises a very large question—one that has been
raised many times—as to whether natural species may not
be hybridization complexes rather than pure line cultures
isolated by some sort of selection, as has been presupposed
since the time of Darwin. I have found that in nature,
crossing, especially between these chrysomelid beetles, is
by no means uncommon, and very frequently results in
adult progeny in nature, some of which have been described
as species. These natural cases of hybridization have
been observed in the last half-dozen years along the edge of
the Mexican plateau. Some other species of chrysomelids,
from the same general region, especially some species of
Labidomera, have a variability strongly suggestive of a
similar origin. JI have found that Labidomera suturella
Chevr., of which many sharply marked variations have
been described, gives a variability in pedigreed cultures
that is strongly suggestive of the species having arisen

Modification of Germinal Constitution of Organisms 199

through a process of hybridization. On the high volcanic
plateau of Toluca there is another type rather closely allied
to L. multitaeniata, which is also suggestive of having arisen,
or of being in the process of arising, through hybridization.

These conditions in nature are of course difficult or
impossible to check and verify, because the past is absolutely
unknown, and little or no indication of what it has been
can be obtained from any source. The materials in muse-
ums and the records by systematists are utterly useless for
this purpose. Apparently the only way of attacking this
problem is the one which I have adopted of placing colonies
in isolated locations, or in cages, there to carry out the
process of interbreeding and forming of hybrid combina-
tions as they would occur in nature.

In the last few years at Tucson a series of experiments
has given an exact duplication of the ‘“‘mutation behavior,”
and further, it is clearly called into operation by conditions
external to the organism. At first a race was synthetized
and was and is still constant, but when placed under opti-
mum conditions of growth and development at Tucson it
has given fourteen distinct types. Some of these had in
previous experiments been tested out and are known to breed
true, and others are still to be tested.

With plants, Gates and Davis are endeavoring to pro-
duce synthetically O. Lamarckiana from a hybridization of
O. grandiflora and O. biennis, and while as yet O. Lamarcki-
ana has not been produced, Davis has obtained a type which
he considers to be very close thereto. It is perhaps not
too much to expect that in the near future O. Lamarckiana
will be experimentally synthetized.

If it proves to be generally true that “mutation behav-
ior’ is a sequence of synthetic composition, it does not in

200 Heredity and Eugenics

any way detract from the value of DeVries’ observations,
nor of the réle which types thus arisen may play in evolu-
tion. It is true that the hypothetical portion of DeVries’
theory as regards a permutation period and so on, is in part
true, in part not. There is a period of synthesis, ending
in a uniform stem race that may endure for a long time, and
subsequently this throws off from itself gametes unlike,
in that there are new combinations of old characters,
reappearance of long latent characters, and not infrequently
new characters.

There is, however, this essential difference between the
conception of DeVries and the one that I have to offer:
namely, DeVries regards species as pure in the old sense
and arising by dichotomy, while I am convinced that prog-
ress will show that synthetic combinations are largely
responsible for the stem forms of generic groups, and that
from these there have arisen related species or types in
greater or less profusion. As far as experience goes, this
production of new types is in the main, if not entirely, a
product of the action of external forces upon the gametic
constitution, although when once started in such a strain
it seems not to cease for some time though the inciting cause
isremoved. In Fig. 70 [have tried to show in diagrammatic
fashion the essential differences of the two conceptions.

B. The Experimental Production of Germinal Variations by
the Direct Action of Different Forces

I. FORCES EXTERNAL TO THE ORGANISM
Incident solar radiation in its various manifestations,
the water relations of organisms, density and composition
of the medium, and the nature of the food stream are the
common groups of forces that are apt to be modified in

201

L Constitution of Organisms

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202 Heredity and Eugenics

presence, character, or intensity, in relation to the organisms,
and to these forces and relations are attributed a variable
value in the production of germinal variations. All kinds
of extreme demands are made upon external forces, from
the conception of an organism as a plastic material which is
pressed into shape, and given its characters by the stress
of environment, to the opposite assertion that environ-
ment acts, if at all, as a minor factor in eliminating the unfit.
From logic and argument no truth may be expected, and
the only hope of progress in the quest for truth in this
problem lies in the domain of exact genetic research.

In this chapter—which is a summary of recent advances
and not a historical résumé of the whole subject—the earlier
work is not discussed, because it has been so often summar-
ized that good discussions of it are available in many
publications. All of the older work, however, is seriously
defective when considered from the viewpoint of present-
day genetic investigations.

IN PLANTS

In the bacteria and yeasts the refined and accurate
methods of investigation now used, and the fuller recog-
nition of the genetic requirements have made possible studies
which have given much valuable information. The work
of Pringsheim, Winogradsky, Hansen, Barber, Beijerinck,
Buchanan, and others stands as examples of what may be
accomplished in the study of this problem in these simple
organisms. In all of the observations thus far made upon
these organisms response to incident forces or changed con-
ditions is immediate, and departures, often of considerable
magnitude in form and function, occur; but in most in-
stances difficulty in fixing these modified characters has
been encountered.

Modification of Germinal Constitution of Organisms 203

The well-organized experiments of Buchanan with Strep-
tococcus lacticus are quite characteristic of the general
results obtained in the investigation of this problem in
unicellular plants. His conclusion that fluctuations cannot
be fixed in bacteria, whether normal or induced, is in accord
with most of the experiments of bacteriologists; neverthe-
less, this result is opposed by many records, believed to be
accurate, of sudden permanent departures in form and
function, especially in the yeasts.

After a comprehensive survey of these studies upon
bacteria, Pringsheim concludes that while changes in yeasts
and bacteria have often resulted from the unusual action of
culture media, toxic solutions, temperature, etc., the modi-
fications of form and activity are diverse, and are either
permanent or transient. Especially difficult, however, if not
impossible in these organisms, is the attempt to separate
somatic and germinal effects, and much reasonable doubt
exists as to its possibility. The important contribution from
this work with bacteria and yeasts is the precise demon-
stration that the departures are readily produced, and
are a direct result of the incident external forces used, even
in the simplest known organisms.

Other low plants, such as algae and fungi, have often
been subjected to exciting agencies, and while changes have
resulted, these, like the modifications in bacteria, are usually
transient and not permanent. It would seem that these
simple forms ought to provide good material for the study of
this problem, although it is possible that the low differentia-
tion between soma and germ may introduce experimental
difficulties yet to be overcome.

In higher plants the observations of Zedebauer with
Capsella are of interest, and introduce observations which

204 Heredity and Eugenics

might be duplicated and extended by proper experimentation
with other plants and lead to new and important informa-
tion. A biotype of Capsella, bursa-pastoris, much lke
taraxicafolium, lives on the low plains along the coasts of
Asia Minor. It has broad leaves, white flowers, and grows
to 30-40 cm. high. On the inland plateau at altitudes of
2,000~2,500 meters grows another form with a stem 2-5 cm.
high, reddish flowers, xerophilous leaves, and an elongated
root system.

From the lowlands roads lead to the plateau, and the
conditions of distribution are such as to suggest that man
has been influential in disseminating this form from the
lowlands to the highlands, where it has taken on the modi-
fied form. Some force to this interpretation of the dis-
tribution is given by the fact that seeds from the plains,
when taken to the plateau, at once assume the somatic
characters of the plateau type. On the other hand, plateau
seeds, planted and grown at Vienna, while they have the
xerophilous character of the leaves, retain the upland char-
acters in flowers, and, to a large extent, in height, root
system, and general habit. It is futile to attempt to draw
from observations in nature such as this conclusions as to
the past history or actual happenings, but such instances
clearly indicate the sort of experimentation that might
profitably be attempted and the type of results that might
be expected.

Much more concrete and accurate are the findings of
Klebs upon Sempervivum, in which inflorescences were
found to be capable of replacement by a single flower, and
many other changes were induced as the result of external,
mainly climatic, forces. More important than the fact
of the departure is the fact that some changes persisted

Modification of Germinal Constitution of Organisms — 205

through three or four generations in properly guarded
cultures.

MacDougal has attacked this problem from a strictly
experimental standpoint in the effort to discover a cause,
and to arrive at an understanding, of the phenomena of
“mutation”? as described by DeVries in Ocnothera. The
method which he has used is to inject solutions of various
kinds into the ovaries immediately before fertilization.
Later, Gager, by subjecting seeds to the action of radium
bromide, has shown that in plants physical factors incident
upon the germinal materials can and do produce germinal
changes that are permanent and persist in undiminished
vigor in subsequent generations.

MacDougal’s experiments, wherein zinc salts, cane
sugar, etc., were injected into the ovules of plants, show
that permanent changes resulted. MacDougal’s method
and the reasons therefor are as follows:

Having carried on pedigree cultures with a large numbe- of species
for several years and having encountered some which did and others
which did not give rise to aberrant individuals, attention was directed
to the possibility of inducing changes in the hereditary elements in
such a manner that the qualities transmitted would be altered or
destroyed. A theoretical consideration of the subject seemed to
indicate that the changes constituting the essential operation of muta-
tion ensued in a stage previous to the reduction divisions in the embryo
sac, or the pollen mother cells. It was planned therefore to subject
these structures to the action of chemical agents, not ordinarily encoun-
tered by the elements in question, at a time before fertilization occurred.
The tests were planned to include the use of a solution of high osmotic
value, and mineral compounds, some of which are toxic in concentrated
solutions and stimulating in the proportions used. The probability
of success would be heightened with the number of ovules contained
in any ovary operated upon, and therefore the common evening
primrose, Ocenothera biennis, Raimannia odorata, a relative of it, and a

200 Heredity and Eugenics

member of the same family, Begonia, Cleome, Abutilon, Sphaeratcea,
and Jfentzelia, and others were experimented upon. Without recourse
to the detail of the work it may be stated that the use of radium prepara-
tions, sugar solutions (ro per cent), and solutions of calcium nitrate,
of distilled water, with capsules of Ratmannia odorata, and zinc sulphate
in a stronger solution used with Oenothera biennis (Fig. 714) was fol-
lowed by very striking results. In the first-named plant, there appeared
in the progeny obtained from a few capsules of one individual several
individuals which were seen to differ notably from the type with the
appearance of the cotyledons, and, as development proceeded, it was
evident that a mutant had appeared following the injections and
nowhere else, which thus had some direct relation to the operation.
The characters of the newly arisen form were so strikingly aberrant
as to need no skill in detection (Fig. 71B). The parent was villous-
hairy, the mutant entirely and absolutely glabrous, the leaves of the
parent have an excessive linear growth of the marginal portions of the
leaf blades and hence become fluted; the excess of growth in the mutant
lies along the midrib and the margins become revolute. The leaves
are widely different in width, those of the mutant being much narrower.
The parental type is of a marked biennial habit and near the close of
the season the internodes formed are extremely short, which has the
result of forming a dense rosette; the mutant forms no rosette by
reason of the fact that the stem does not cease, or diminish its rate of
elongation and hence presents an elongated leafy stem, which con-
tinues to enlarge as if perennial. The first generation of the derivative
came to bloom; the flowers of the mutant were closely guarded and as
soon as seeds were obtained they were planted to obtain a second
generation. A few plants were obtained, which in every particular
conformed to the new type and exhibited no return to the parental
type.

MacDougal’s investigations, wherein were produced
modifications that have remained stable through four or
more generations, in Ratmannia, Cereus, Penstemon, and
others, show fully that the method employed gives definite
changes in germinal constitution.

Modification of Germinal Constitution of Organisms 207

Fic. 71.—Two plants of Onagra biennis, showing the effect of injections of
zinc sulphate into the ovule. A, normal. B, the modified plant, which arose
from seeds that had been modified by the zinc sulphate. (From MacDougal.)

208 Heredity and Eugenics

In Gager’s experiments the action of radium rays and
emanations upon plants are definite, and in some instances
permanent modifications resulted (Hig. 72). In these
experiments modifications by physical and chemical agents
were produced which are not necessarily pathological, and
some of them continued to breed true in subsequent genera-
tions.

Gager found that the action of radium rays upon pollen
cells was to produce distortion of the karyokinetic figure
to the extent that chromosomes were left entirely out of
the spindle and were lost to that particular germ cell.
What happens in any particular variant whose modifica-
tions are inheritable has not been determined, but the sug-
gestion is at least plausible that the radium emanations in
some way produce a new, or bring about a rearrangement
of the physiological complex which exists in the germ cell.
Conceivably it may be due to the displacement of an indi-
vidual chromosome, although this suggestion would need
verification before it could be adopted.

The modifications induced by the injections of salts
in MacDougal’s experiments are not easy to understand.
The cells of the ovule are relatively impervious, and there
is a relatively small amount of dispersion from the seat of
the wound. The results obtained, however, are not due to
the effects of wounding, as shown by the fact that ovules
wounded in the same manner do not produce modifications
unless the salts are present; likewise, ovules stung by insects
do not, as far as known, produce these results, and it is
only in ovules into which chemical salts have been injected
that modifications are effected. The conclusion seems un-
avoidable that the salts injected produced the observed
results by modifying in some way the constitution of the

Tic. 72.—Showing effects of
rays of radium upon plants.
(From Gager.) The plants in
this case are Onagra biennts,
showing arrested development.
The ovary was exposed to
radiations of radium bromide
(10,000) in a sealed glass
tube for 53 hours.

210 Heredity and Eugenics

germinal substance. MacDougal’s general conclusion, as
to the manner of producing this result, is that the action of
the injected chemicals is to accelerate or retard processes,
especially those of a katalytic nature within the germ cells,
or possibly, actual chemical changes in germinal substance
may be affected.

IN ANIMALS

In animals the most satisfactory results have been
obtained with higher types, while among the lower types,
Protozoa, for example, changes by incident forces, though
capable of production, behave in much the same manner
as do changes induced in bacteria and yeasts. In some
instances, variations persist for many successive fissions, but
they usually occur in only one of the individuals of each pair,
as in Jennings’ Paramoecium with a spine. In these in-
stances there is little or no spread of the change in the popu-
lation through reproduction and thus far no long-continued
strains have been developed through these agencies. The
condition of protozoans in the non-differentiation of soma
and germ, as in bacteria, is a complication not easily over-
come in experiment, and it may well be, as has been often
suggested, that the entire organism is the “germ plasm.”

Attempts to produce germinal changes by the direct
action upon the germ of external agents have not been made
by many workers. Many, it is true, have subjected organ-
isms to changed conditions and obtained modifications,
aberrations, but relatively few tests have been made to
determine the inheritability of these changes.

The recent experiments of Woltereck with Daphnia
and Sumner with mice are good examples of a common
type of investigation, Woltereck carried strains of Daphnia
in cultures in which over-feeding was practiced for about

Modification of Germinal Constitution of Organisms 211

two years. At the end of this period it was found that the
head form had changed and that when the modified form
was put back into the original conditions the changed form
was retained. Unquestionably, in Woltereck’s cultures a
head form, different from the one with which the culture
started, was present at the end of two years, and this did
not revert on return to normal conditions; but the failure
to carry adequately controlled parallel normal lines does
not permit a decision as to whether the change is a real one,
or due to the progressive selection of a biotype present
but obscured in the original population. Nor do the
experiments permit of a decision as to whether the effects
observed were due to direct germinal modifications or to so-
matic transmission. It is shown that a permanent change
of the race resulted, and nothing more. Parallel cultures
and much more careful experimentation would be necessary
in the effort to answer the more important points.

Similar in method and in results are the experiments and
conclusions obtained by Kammerer on certain amphibians
and Lacertilia. For example, Salamandra maculosa is
ovaviparous in the lowlands, but its highland variety,
S. atra, is viviparous, and the larvae are large when born
and have long gills. It was found that lowland forms of
S. maculosa kept without water at low temperatures showed
reproductive habits and young much like those in S. atra
in the alpine regions. In the lizards, temperature was
found to be productive of color changes, giving dimorphism
in the males of one species and in the females of another.
These changes are alternative in crosses.

In both experiments the results have not been carried
far enough to test the inheritance thoroughly, and moreover,
the conditions of experiment do not permit of any analysis

212 Heredity and Eugenics

of the process at the bottom of the observed changes. In
both, there are changes following altered conditions, and
there have resulted changes in the organism which are
known to occur in many instances, only in these experi-
ments some effort was made to test the permanency of
the variation and its behavior in subsequent crosses. In
both, the change seems to be a germinal one, as is indicated
by its behavior in inheritance. Whether the change is a di-
rect germinal or an indirect one, due to somatic influence or
transmission, the experiments cannot decide.

Precisely similar are Sumner’s experiments in sub-
jecting mice to high and low temperatures, where at the
end differences were found which were attributed to the
effect of the different conditions. Differences there were
at the end, but in mammals so variable as mice carefully
pedigreed strains free from biotypes should have been used,
and adequate parallel controls should have been main-
tained. In that controls of critical character were lack-
ing and the possibility of biotypes was not eliminated from
the stock used, the results obtained are easily attributed to
gradual selection of biotypes or of actuation of latent
characters, as well as to the effect of changed temperatures.
As for the question of somatic influence or direct germinal
effect, the experiments are not conducted so as to give proper
evidence thereon and are capable of any interpretation.
The experiments show, however, that changed conditions
changed the stock, which change may have resulted from
any of the methods suggested, and the change is appar-
ently permanent although the series was too short to answer
this question adequately.

In insects, I have obtained modifications in various
ways, some of which will be described in a later portion

Modification of Germinal Constitution of Organisms 213

of the chapter. Morgan, in Drosophila ampelophila Low,
found that sex-limited variations of pink eye, etc., have
apparently followed the treatment of cultures of this animal
to the action of radium bromide. Loeb, however, using the
same organism, found that in both experiment and control
the variation described by Morgan appeared, and of course
concluded that the tendency to produce this variation was
already present in the race of flies used.

Lutz had for several years used the same strain of
Drosophila for experiment, and found much variation in wing
venation. He also subjected the strain at times to different
experimental conditions, and this may be responsible for the
appearance of the variation found by Morgan following the
use of radium, and which appeared in experiment and control
in Loeb’s experiments.

In Chrysomelid Beetles

In the modification of the germinal constitution by
experimental means it must be known as certainly as is
possible whether there are in the germ potential capacities,
i.e., latent characters, which ordinarily are not visible in
the materials used, but which may be called into visibility,
periodically or rarely, by unusual conditions. Unless pos-
sibilities of this kind are eliminated, it becomes difficult
in experiment to decide whether observed results are the
product of latent conditions, or of the experiment as de nove
variations. Moreover, experiments to show the effect
of incident conditions upon the germinal material must,
beyond any question, show that the effect is primarily
upon the germ and not first upon the soma of the parent,
and secondarily, by transmission, to the germ. If, in
experiment, the soma of the parent and of the resulting

214 Heredity and Eugenics

progeny be modified in the same manner, there are two
possible explanations. The incident conditions may modify
both soma and germ independently, and they would be
similarly modified because both soma and germ represent
one and the same group of potentialities; or the observed
results can be explained by assuming that incident conditions
first modify the soma, and secondarily, through transmission,
the modification is incorporated into the germ cell; and
thus be interpreted as upholding the neo-Lamarckian idea
of the inheritance of acquired soma variations. It follows,
therefore, that the germ cells upon which experiments are to
be carried out must either be taken from the body of the
parent and placed in indifferent media before being experi-
mented upon, or they must be in organisms that can under-
go no further somatic modifications. In this there could,
of course, be no transmission of acquired variations, because
no variations are acquired. Moreover, for our purpose
any resulting change must be thoroughly tested by subse-
quent breeding for many generations.

When these organisms attain sexual maturity, they have
attained all of the somatic modifications, save pathological
growths, which it is possible for them to achieve; the onto-
genetic development of variations has come to a standstill,
the whole activity of the organism is directed to reproducing
the species, and further development or divergence in any
of its attributes or qualities is forever inhibited. Whatever
changes occur, from sexual maturity onward, are pathological
or senescent.

It is possible, therefore, to chminate from these experi-
ments the neo-Lamarckian factor, because the conditions
of experiment were not applied until after the parents had

Modification of Germinal Constitution of Organisms — 215

attained full sexual maturity and complete development
of all qualities and attributes.

A check upon the possible latent characters is more
dificult, but in this material it is easily carried out in one
of two ways: First, only pedigreed material was used in
experiment. This material has always been tested by cross-
ing within and without the species to discover, as far as
possible, any characters which might be present in invisible
conditions. Thus far, no attributes of this description have
been discovered. Second, a check was kept upon this
possible source of error in the following way: these beetles
have the habit of maturing their eggs in definite rotation;
that is, a batch of eggs is developed, fertilized, and laid;
then a time interval elapses during which another batch of
eggs is being developed, and this is repeated many times,
thus giving isolated lots of eggs, each separated from the
one before by a time interval of from two to sixty days,
or even more, and any one of which may be subjected to
experiment and the others used as controls. In many of
these experiments color has served as a useful character for
study and the results from the experimental modification
of color may be presented first.

Experimental modification of color.—Color modifications
are of two distinct kinds: changes in the pigment itself,
and in the localization thereof. The first is a chemical
change produced by a rearrangement of the chemical
activities existing between a chromogen and an enzyme
which brings the color-forming compounds into existence,
while the latter is a change in the localization.

Variations in color usually are either accentuations or
diminutions of existing color, and these changes are perma-

216 Heredity and Eugenics

nent, are not pathological, and the individuals possessing
them are by no means weaklings, which has been shown in
the case of L. pallida (Fig. 73B), which was produced in
considerable numbers as a variation of L. decemlineata Say,

Fic. 73.—Some divergent types of beetles produced by subjecting the germ
cells to external influences. A, normal decemlincata. B, the form pallida. C,
lortuosa. D, defecto-punctata.

in some of my earlier cultures. This modification represents
definitely a decrease in the pigmentation values of the organ-
ism, with slight changes in bodily proportions, punctation,
habits, etc. It arises by subjecting the organism to rigor-

Modification of Germinal Constitution of Organisms 217

ous conditions, especially high temperature accompanied
by low relative humidity. Such variants have been found
in nature, some of them are known to breed true, and
others are produced in experiment.

Fig. 74 shows a photograph of a demonstration case
exhibiting the results from an experiment of this kind.
Here the parent pair are shown producing the two first lots
of eggs which developed into normal individuals which
were in following generations true to type, while the third,
fourth, and fifth lots of eggs were experimented upon and
gave in each modified types, pallida and minuta, as well as
some normals. These different types, when inbred, came
true to type in subsequent generations, as shown.

Another divergent type which arose in the same series
of experiments is one in which the pigmentation is increased,
that is, the amount of dark pigment in the color pattern
gave the resulting individual a different appearance from that
of the parent species. Both pallida and melanicum (Fig.
734) were true breeding germinal variations, and pallida
when given a fair start showed itself, at least in certain
cultures, to be capable of sustaining itself in competition with
the parent species; melanicum, however, did not exhibit any
such potentiality.

Ii a form like L. pallida were to develop in an arid area
it would be recognized, as I have suggested, as a step in the
process of evolution, and it would be directly attributed, if
it were found in nature, to the conditions under which it
was living, and its existence would be explained either by
natural selection, or some other of the current hypotheses.

Other modifications which have arisen from L. decem-
lineata, especially in the modification of the hypodermal
lipoid pigments, are distinctly not the increase or decrease

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Fic. 74.—Photograph of demonstration case which has been arranged to
show the effects produced upon the progeny of a single pair of beetles by subjecting
the ova to strong incident physical forces, before and during fertilization. To the
left is represented the normal stock, showing no presence during the time of experi-
ment of the modified forms. The first two lots, A and B, were laid and matured
under normal conditions and gave normal types. Lot C, laid and matured under
the conditions of the experiment, gave part modified and part unmodified forms.
The same is true of Lots D and E. The modified types in this experiment were
mainly pallida, clearly distinguishable in the photograph by their lighter and
smaller form; they breed true in successive generations as indicated in the
demonstration case.

220 Heredity and Eugenics

in the amount of pigmentation, but represent the rapid
changes which are characteristic of lipochrome pigments:
for example, in rubrivittata, in which the most striking
character is the bright red hypodermal color. This arises
suddenly as the result of experimental conditions and
reproduces itself when bred back to the parent species,
giving a color segregation into rubriviltata and hybrids, the
rubrivittata breeding true. The behavior of rubrivittata
is such as to suggest that in its main distinctive character
it is recessive to the parent species.

In modifications of color we are dealing with superficial
chemical processes in the organism—the development of a
chromogen and the oxidation of that chromogen by one or
more oxidizing enzymes to a state of stability where simpler
compounds are produced which are productive of color.
In no experiments in the modification of color, especially
in colors such as the melanins, etc., has any modification
been produced which is not an accentuation or diminution
of the oxidative capacity of the organism. That is, in
the case of pallida, there is a decrease in the capacity of the
organism to produce either (1) the necessary oxidizing
agents, or (2) the requisite amount of chromogen, or (3)
the capacity of the organism to sustain the conditions
necessary for the oxidative processes a sufficiently long
time to enable a given amount of chromogen to be oxidized
to produce a stated amount of pigment.

It has long been known that the series of color changes
may proceed from white, through yellowish, yellowish-
brown, reddish-brown, deeper browns, and finally to black,
then to a still further stage of oxidation—white, so that
with a given amount of chromogen and a given amount of

oxidizing enzyme, diverse results can be obtained from

Modification of Germinal Constitution of Organisms 221

identical materials, simply by the duration of time which
the process is allowed to act. This can readily be shown
in any of this material in the ontogenetic development of
the individual. The oxidative process may be stopped at
any stage, and the coloration of the organism then remains
at the stage in which the oxidation was stopped. On the
other hand, the process may be continued for an abnor-
mally long time, producing an unusual amount of pigment
substances, giving the organism a dark appearance.

We are ignorant of any mechanism in the germ cell
which would bring about such inhibition of the oxidative
process, supposing that the amount of chromogen and
oxidizer remains the same. Of course one could, in explain-
ing this condition, adopt the idea developed by Davenport
of the existence of inhibitors, and while it is highly probable
that there are such inhibitors present in the germinal
mechanism, information concerning them is so fragmentary
that any extended use thereof in explaining these phenomena
would better be postponed.

The interpretation of the results produced is that the
germinal complex has been permanently modified in some
way, such that either the chromogen is not present in
sufficient amount to produce the color of the parental genera-
tion, or the oxidation is deficient, but which of the two
possibilities is correct cannot at the present time be decided.
It is entirely probable that it might be one in some instances
and in another the other factor that was deficient, both
conditions bringing about identical results. It does not
follow from this that there exists in the germ a definite
representative of the chromogen and of the katalytic agent.

In the germ cells, as in all other cells, oxidases and sub-
stances which may serve as a chromogen are present and

222 Heredity and Eugenics

this capacity, therefore, for the production of pigmentation
is not something which is conditioned by any particular
thing in the cell, but it represents a capacity common to all
living substances.

In what way is the constitution of the germ cell
modified so that the organism shows in subsequent gen-
erations a permanent change in its coloration? It has
been pointed out to me by Professor Morgan that in these
experiments the behavior in the first generation is difficult
of interpretation. In these experiments the male cells
or the female cells, and sometimes both, have been sub-
jected to conditions of experiment at a susceptible stage.
Eggs are most susceptible immediately before and during
maturation, although what connection this has to the
maturation process is not known.

Morgan has raised the question, why do individuals, de-
veloped from eggs which have been subjected to conditions of
experiment and fertilized with normal sperm, not give a sub-
sequent hybrid behavior ? No hybrid splitting has ever been
found in any of my experiments, or in those of MacDougal
or Gager. The resulting modification reproduces itself true
to type, and does not give subsequent splittings suggestive
of the combination of different factors or unit-characters.
If there are unit-characters, it is logical to expect that in
experiments of this kind the experiment would modify
the unit-character in the germ plasm, and that this modified
unit-character would then behave, when crossed with its
normal homologue, exactly as hybrids do in other cultures.
The total lack of this behavior in my experiments, and those
of MacDougal, Gager, and others, might be considered
good evidence that there are no such things as_unit-
characters, nor in the germ cells any potentiality capable

Modification of Germinal Constitution of Organisms — 223

of individual removal or behavior. Any such deduction,
however, is unwarranted and contrary to known facts, and,
furthermore, these modified characters themselves show that
after establishment they are alternative and capable in many
instances of replacement and recombination in full conform-
ity with established principles of heredity behavior.

How shall this behavior, which has been observed by
MacDougal, Gager, myself, and others, in the production
of these variations, be interpreted? MacDougal’s inter-
pretation, in the case of plants, is that the modifications
induced are due to the modifiability of the enzyme action
in one way or another. Gager attributes the activity to
the derangement of the chromosomes by the radium emana-
tions. In beetles, I do not know that the chromosomes
are deranged by any of the processes, and we do not know
that the chromosomes are the specific bearers of any par-
ticular attributes. The explanation which appeals most
strongly to me in the case of eggs which have been subjected
to strong incident forces is that the change should be
regarded as an example of stereoisomeric change, whether in
the composition of the katalyzing agent, or in the composi-
tion of the chromogen, or in some accelerator or inhibiting
agent in the germ plasm. It is quite conceivable that the
change may take place in the chromogen. As far as known,
all chromogens are substances of wide distribution in all
organisms with slightly different chemical characteristics,
and it is highly probably that there is a wide range of
chemical composition in these chromogens, so that a slight
change in the arrangement of the molecular composition
of the chromogen could be productive of the results observed.
At present, however, there is little possibility of obtaining
definite evidence along this line, because the present methods

224 Heredity and Eugenics

of physiological chemistry are so exceedingly gross that
when by any available method either chromogen or enzyme
have been removed, they have been changed to a very
considerable degree in structure and relations, and possibly
in capacity for pigment production. The complexity and
almost futile nature of the chemical side of this problem is
clearly indicated by the statement (Meischer) that in
albumen molecules containing no more than forty carbon
atoms there are something like a billion possible stereo-
isomeres. It is at once evident how utterly hopeless it is
with present methods to expect exact chemical determina-
tions of these germinal changes, and the best that the
physiological chemist can be expected to do is to show the
grosser outlines of the possible processes involved. To
determine the exact changes within the germ cell is at
present not possible.

Furthermore, the results of Reichert and Brown upon
the investigation of haemoglobin crystals have shown a great
array of crystalline forms and structures in this substance
in allied mammalia, and it is highly probable that other sub-
stances throughout the organic world are equally divergent,
equally complex, and equally specific. We must therefore
keep in mind that in these color modifications there are
always three possibilities—the modification of the chromo-
gen base, the modification of the enzyme, or the modification
of the capacity for carrying on the process; but present evi-
dence, I believe, warrants a stronger belief in the efficiency
of modifications in the capacity of carrying on the process
more than in the modification of either the chromogen base
or the katalyzer, i.e., to modified accelerators and inhibitors.

In colors due to lipoids, modifications thereof might be
attributable to changes in the chromogen base, in the

Modification of Germinal Constitution of Organisms 225

katalyzer, or, in some cases, perhaps, to the stereoisomeric
relations in the molecules which are attached to the fatty
base. The well-known changes which are possible in the
case of lipochrome colors, changing with sharp alternative-
ness from red to yellow, from orange to white, or vice
versa, are quite possibly due to reversibility in some enzyme
within the germ cell, and this reversed action remains
reversed until such time as it is again changed in its direction
by incident factors. That this is apparently the correct
explanation of the behavior of this particular type of
pigmentation activity seems to be fully shown by many
experiments.

In many of my experiments germ cells that were pro-
duced at a time when the lipochrome pigment in the parents
was yellow, produced yellow progeny, but when the color
had been experimentally reversed they gave white, orange,
or red progeny, depending upon the direction of change in
the parent. These results strongly indicate that the inter-
pretation which I have placed upon this type of germinal
variation is the correct one.

Variations in these lipoid color characters are common in
plants and animals, and characters based upon these are
widely used as specific differentials, and they are permanent
so long as a given state of equilibrium exists. This state
of equilibrium, however, can be reversed or upset, producing
reversed conditions, and these reversed conditions can again,
after an indefinite period, be brought back to the first
condition, or some other condition, by incident forces. It is
almost heresy at the present time to suggest the possibility
of reversibility in evolutionary action, but the reversible
nature of many characters of importance in evolution is by
no means unthinkable and is susceptible of experimental

226 Heredity and Eugenics

investigation. The dogma of the irreversibility of evolution
processes, which has grown out of phylogenetic and onto-
genetic study, is incompatible with a physico-chemical in-
terpretation of nature, and has no basis at present in critical
experimental investigation.

These germinal modifications of color characters indicate
an approach to an understanding of germinal variations in
certain attributes; that is, it is understood what might
happen, but in no case is it known what did happen, nor
how. These variations in color concern superficial attributes
in the economy of the organism; and the mere production
of a color-producing substance is to a greater or less extent
only an incident in the life of the organism. Colors are
produced pathologically or otherwise in these organisms,
by wounding, by disease, etc., at will, showing that there is
throughout the organism the capacity for the production
of color compound which lies at the basis of the normal
coloration. The greater problem lies not in the production
of color changes, but in the processes which are productive
of the localization of pigments into a color pattern, and it is
this attribute of pattern which differentiates organisms most
certainly from inorganic substances. What is it that is
productive of pattern, and in which way may the color be
modified ?

Experimental modification of pattern.—The pattern is an
attribute by no means so easy to modify as is color, but it
has been found that the pattern is less modifiable by incident
forces than other parts of the organism. Of those instances
in which the pattern has been modified, as in albida, tortuosa,
minuta, and defecta punctata (Fig. 73C), all proved to be
germinal variations and to breed true, but the difficulty in
breeding many of them and their inability to exist under

Modification of Germinal Constitution of Organisms 227

the conditions into which they were born lead one to
conclude that what is actually produced in many of these
modifications are pathological germinal variations, rather
than healthy germinal conditions which can be perpetuated
indefinitely in nature. It should further be noted that in
these modifications the changes were essentially in the
amount of pigment which was produced in definite areas,
especially in the color pattern of the pronotum and elytra,
and while the change existed through the body as a whole, it
is not thereby established that the fundamental pattern
upon which these attributes are based was in any way
altered. All that is certain is that there was produced a
permanent modification of the capacity to produce pigment
in the form of spots or stripes in definite areas.

In these modified organisms the capacity to produce
pigment is by no means absent, as for example, in albida,
where dark color could be subsequently produced upon any
part of the body by wounds, etc., giving a considerable
amount of the same dark pigment in the hypodermis and
in the lower layers of the cuticula. The capacity to
produce both the oxidizing agent and the chromogen is
present, but the pigment is not produced in a definite loca-
tion; in other words, whatever it is in the organism that
determines localization is inactive, and pigment production
is inhibited by some unknown inhibitor.

The production of variations in pattern by means of
intense stimuli has not, in my experience, been accompanied
by what I regard as conspicuous success. Variations have
been produced, but these variations are often of a pathologi-
cal character and could not be produced under the condi-
tions imposed by nature. Permanent variations, however,
in the pattern are obtainable by a combination of external

226 Heredity and Eugenics

forces with selective accumulation, provided the impact of
the external forces is not made too intense. In other words,
variations properly combined lead to more definite results in
the modification of pattern than the more vigorous methods
which are productive of permanent changes in color. It is
therefore necessary to distinguish between the modifications
of color and modifications of color pattern, because pat-
tern may well be present as an attribute without revealing
itself, and it only reveals itself when something in the
organism results in the deposition of color in the proper
location.

In the experimental modification of organisms, the pat-
tern has been one of the characters least influenced. In
DeVries’ experiments with plants the pattern was modified
relatively little, if at all, the principal changes in Oenothera
being in leaf proportion, leaf arrangement, color, and
similar characters, which are properties of the whole and
which are known to vary with more or less readiness in all
organisms. In the same way the experiments which have
been carried out on insects by Dorfmeister, Weismann,
Fischer, Edwards, Standfuss, and many others, show modi-
fications in the color and little or no modification in the
pattern. In some specimens the pattern is obscured by the
spreading of the color from the original area into contiguous
portions, but the fundamental pattern itself is not altered,
as shown by the fact that in most of these experiments in
the next generation the progeny revert to the pattern of
the normal parental stock.

In MacDougal’s experiments with plants, and in Gager’s
also, the pattern appears to be only slightly modified, if at
all, and in all of the plants used by them the pattern was
relatively simple, both petals and leaves being self-colored,

Modification of Germinal Constitution of Organisms 229

and the variations which occurred were mainly variations
which resulted from modifications of the growth processes,
influencing leaf proportions, and such characters as pubes-
cence, color, etc.

In experiments with beetles, I have found that the
subjection of organisms to unusual environmental stimuli
did not as a rule materially change the pattern, and never,
as far as I have observed, did it in any way alter the funda-
mental pattern basis of the organism. It might appear
on superficial inspection that the pattern existed in its origi-
nal simplicity, even if it were not manifest to the eye. For
instance, in defecta punctata, it is the inability of the pigment,
through some cause or other, to be developed in particular
areas. This inhibition of pigmentation may be due to the
oxidizing of the pigment to a colorless state. On the other
hand, in variations like melanicum, in which the color pat-
tern of many of the parts is distinctly different, as far as
superficial inspection is concerned, the underlying pattern
is unaltered, and that which goes to make up the difference
between melanicum and the parent species is simply added
development and extension of the color from the original
areas around which they develop. This is shown by the
fact that during the ontogeny in melanicum there is an
exact recapitulation of the stages through which melanicum
has passed in reaching its present state. This represents
an accentuation of existing characters along definite lines.

Tn variations of another kind there are indications that
fundamental changes in the pattern occur. L. melanothorax
Stal, bears a relation to the species L. multitaeniata Stal
either of a constantly recurring mutant which is unable
to survive the conditions under which it arises, or may
represent the constant reappearance of a species which

230 Heredity and Eugenics

has been absorbed by multilaeniata, but not completely
incorporated—traces of it occurring in every generation
with greater or less frequency. Both the melanothorax
and multitaeniata develop among the progeny of the same
parents, and between them there is a striking difference in
the development of the pattern. Both start from essen-
tially the same base, but meclanothorax diverges with great
rapidity and does not pass through the stages of the parents
from which it came, as shown in Fig. 75.

<* Mey. Be ~_ anal

; A 2 ate, See ee
ED NG

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ais, ph fie

Ug ae ie, / Fr £ saa

eae

{ cite Soican

lic. 75.—To show the sequence of stages in ontogeny in L. multlitaeniata (A)
and its recurrent mutant, melanothorax (B). It should be noted that the latter
form has its own type of development and diverges from the parental condition,
having very little in common with LZ. multilacniata from which it came. This

a)
e
ye
=
‘e

P

suggests that this type of development is as much a specific and independent
character as is its final form.

In a pure strain of L. multitaeniata Stal, where no traces
of melanothorax were observed for several generations,
injections of dilute solutions of calcium nitrate caused it
to give melanothorax. In these induced forms the ontogeny
of the color pattern is the same as in the development of
material found in nature. This behavior of melanothorax
represents another type of pattern modification—a rapid
divergence from the initial state common to a very wide
range of species, and in no wise is it a repetition of the

Modification of Germinal Constitution of Organisms 231

ontogenetic history of the parent from which it came. In
view of the fact that the real relation which exists between
L. multitaeniata and L. melanothorax must remain unknown,
no conclusion as to the significance of this wide divergence
in the development of the color pattern can be safely
drawn. The relation between L. mutltitaeniata and L.
melanothorax may be that of two hybridizing species in
which L. melanothorax is in the process of assimilation, and
if this attribute is a ‘“‘unit-character”’ it follows that in the
reappearance of the recessive form which L. melanothorax
appears to be, it is to be expected that the recessive char-
acter would exhibit the ontogenetic series of stages charac-
teristic of itself, and not those of the parent species out
of which it came. There is, however, another possibility,
namely, that the reappearance of L. melanothorax in each
generation of L. multitaeniala may be considered a recurring
mutation which diverges in its direction independently of
the parental type.

This observed condition can be explained on the basis
of multifarious mutations in the sense of DeVries, or on the
basis of unit-characters recessive to L. mudltitaeniata, but
recurring with greater or less frequency. Under condi-
tions of nature it is not possible to determine which one of
these two possibilities is the correct one.

2. HYBRIDIZATION

The results obtained by the horticulturist and husband-
man through hybridization in achieving the modifications
of plants and animals which are desired have long been
known, and in plants a very considerable array of the modi-
fications produced never get beyond the first hybrid genera-
tion and are perpetuated by cuttings, or other forms of

NS
WwW

Heredity and Eugenics

is)

asexual reproduction. In animals a considerable array of
domesticated forms are definitely the product of hybridiza-
tion. Poultry, for example, are derived from two or three
original stocks which have been intercrossed numberless
times, and from these crosses have resulted variations in
the arrangement of the parental characters and combina-
tions of characters. The same is true of domesticated
pigeons, where hybridization has been carried out to a very
great extent, and in dogs, cats, mice, rabbits, rats, guinea-
pigs, swine, and in practically all domesticated organisms
essentially the same condition exists. Unfortunately, in
domesticated organisms the beginning of these modi-
fications is shrouded in antiquity, and while man has
reared dogs, swine, pigeons, and poultry for a long period,
and while there have arisen under his hand the variations
which are now seen under domestication, the manner of
origin is unknown, and the best that can be done is to
make plausible guesses as to what the procedure really was.

The modification of both wild and domesticated stocks
through hybridization is well known to all students of
hybridization, and these modifications are of two general
categories: First, the production of new combinations of
existing attributes, and second, the origin of de novo varia-
tions based upon the attributes of the crossed stocks. The
first is by far the most common change, and the second
is relatively rare in occurrence. I may illustrate the
results produced in these two kinds of modifications by
crossing, by examples taken from my cultures.

L. signaticollis has in the full-grown larvae one row of
black spots on the dorsal side, with a deep chrome-yellow
body color, and in the adult the elytra are marked with
irregular rows of impressed punctations with a deposit of

Modification of Germinal Constitution of Organisms — 233

black pigment at the bottom of each. By a process of
hybridization and extraction it is possible to obtain a race
of signaticollis which, if found in nature, would be regarded
as a distinct species; and when it occurs in experiment it
behaves with the same sharp alternative distinctness of any
natural species.

If a female of L. wndecimlineata, which has the larval
ground color white without any black spots on the back,
and with one row of black spots surrounding the spiracles
in the adult larvae and the impressed punctations very
regular in pattern with the rows closely parallel, is crossed
with a male of L. signaticollis, the F, generation gives two
types of larvae (yls) and (wis), in the proportion of 1:1.
From the (yls) larvae will come a type intermediate between
the two, and this type, when inbred, gives in the second
hybrid generation four types of full-grown larvae (ws),
(whS), (ylS), and (yls). From the (wis) larvae in the
second generation are obtained three classes of adults: like
the female parent, L. undecimlineata, like the male parent,
L. signaticollis, and intermediate between the two.

If, now, a cross be made between these extracted F, un-
decimlineata types with the extracted F, signaticollis type,
we get in F, mature larvae which are (wiS), and these
give mid-type adults in which the elytral punctations are
arranged in closely parallel rows like the wndecimlineata
type. These, when inbred, give in F, larvae which
are (whS) like the wndecimlineata type, and these larvae
give three types of adults: like the wndecimlineata type, a
mid-type, and like the signaticollis type.

The signaticollis type which comes out of these crosses
is the modified signaticollis type, and these, when inbred,
have a life cycle shorter than is normal to signaticollis.

234 Heredity and Eugenics

Its larval stages are totally different from the larval stages
of signaticollis, and the general appearance of the organism
is totally different. This type, derived from these variations
by a series of hybrid modifications, if placed side by side with
the normal species is so strikingly different that if found in
nature no one would hesitate for a moment to designate it
a distinct Linnean species. Not one of the characters in
this form is new, and each is directly traceable to one or
the other of the parents—but the form shows a new arrange-
ment of these attributes.

In this species a germinal modification, obtained through
hybridization, resulted, in which a rearrangement of
attributes produced new combinations which are stable
under the conditions of existence. It cannot be said in
this case that anything new has been produced, only that
existing characters have been rearranged and produced a
combination hitherto unknown. This is the commoner
type of modification through hybridization; there are, how-
ever, other types of changes which are still more interesting.

3. BY COMBINED SELECTIVE CONCENTRATION AND
HYBRIDIZATION

A good example is found in a series of experiments
recently carried out, in which L. undecimlineata was crossed
with ZL. signaticollis of the modified 419 stock, but with
these differences. There is a tendency in certain races of
L. undecimlineata for the ramous stripe to be broken about
one-half its distance from the anterior end. The break in
this stripe is fairly common, but is something which is
not really fixed in this species, at least by means of any
known process; that is, it cannot be rendered a permanent
invariable character, but a race can be created in which the

Modification of Germinal Constitution of Organisms — 235

attribute is present in a higher proportion of individuals
than is normal. Such a race was created by means of
selection in which about 60 per cent of any generation would
have the modification and the other 40 per cent would
be without it. These proportions, however, have no sig-
nificance because those possessing it were just as liable not
to be able to transmit it, and those that did not possess it
were just as likely to have it show up in their progeny.

The szgnaticollis stock had further been modified by a
selective process in that the amount of black pigment upon
the impressed punctations had been considerably increased
and by selection the impressed punctations had been
brought to a state where they existed in irregular parallel
rows. In the extreme of this selected stock which is not
constant, the appearance of the elytra is often that of two
closely placed irregularly parallel black lines. There is
an increase of pigment which finally continued from one
punctation to another, making a continuous line, in place
of a series of broken dots.

These two stocks, modified by selection, were crossed
and gave in the first hybrid generation two types of adults:
a mid-type and one like the female wndecimlineata type.
The mid-type, when inbred, gave four classes of full-grown
larvae, (whs), (whS), (yLS), (yls), and from each of these
there developed three classes of adults, characteristic of
such hybrid operations. In the three classes of adults
developed from the (yls) larvae in the second hybrid
generations are found a variable number possessed of a
combination of the selected characters of the parents;
that is, individuals which in normal crosses are of the
undecimlineata type, with the elytral stripes present as
one single solid band, in this cross have two narrow

230 Heredity and Eugenics

parallel bands. A double-striped condition in place of a
single stripe.

Many of the mid-types exhibited the same modifica-
tion to a lesser degree, especially the break in the band.
A female of this double-striped character was mated with
an extracted male wndecimlineata (a brother), and when in-
bred there were obtained in the next generation adults with
the elytral stripe single, the elytral stripes single and broken,
double, double and broken. From these it has been pos-
sible, by a process of analysis, to develop the following stable
combination: a type in which the larva is white with large
black spots upon the back like the larva of signaticollis, but
with the ground color white, and with the elytral stripes
double in the adult; the same type with the stripes double
and broken, and the same type but with the ramous and
first costal stripes also broken. Third, the same type of
larvae, but with all of the stripes broken. The elytral
stripes are extremely invariable and most difficult of modi-
fication, but this example shows clearly that by combining
in the process of hybridization characters accentuated by
selection—and it will probably be true of characters accen-
tuated in any other way—that there is a definite increase
in the modification of characters and that they are rendered
stable in the constitution of the gamete and might easily
take part in tne formation of species. Figs. 764-G show
some of the types thus far obtained from an evolution
movement initiated by the process described.

In these experiments the modifications are in no wise
due to the influence of external factors; in fact, they were
carried out under relatively constant condjtions, nor is it
conceivable that external factors could be productive of such
a result. What it is that has brought about these modifica-

Fic. 76.—To show certain new types that have recently been produced by
certain processes.

i)
On
~

Heredity and Eugenics

tions we have no means of knowing until more is known of
germinal constitution. It is clear, however, that by hybridi-
zation it is possible to bring about permanent modifications
of pattern, and these are not only modifications of color
pattern but also of the pattern of the structures, as for
example, the punctations, venation, etc. These latter
attributes are, by systematists, considered as characters
of prime importance, and are made the basis of innumerable
systematic distinctions, but in these experiments they
are as susceptible to changes, derangement, and de novo
variations as are the characters which are based upon color,
and color arrangement. In our present ignorance of the
nature of the localizing process in any material, either living
or non-living, we are left entirely in the dark as to what
actually goes on. The experiments, however, suggest the
manner in which modifications may result, and these
resulting modifications may well be productive of evolu-
tion changes either of advancement or regression.

4. BY SELECTION

DeVries correctly maintains that the quantitative
accumulation of small variations will be productive of a
modification which will move rapidly in a given direction
until the limit is reached. This can be demonstrated in
many plants and animals for a number of characters. The
manner in which quantitative accumulation operates is
well shown by the following examples:

T attempted by selection to create an albinic race of L. decemlineata
in two ways—first, by selecting for breeding the most extreme albinic
variations found in nature, and second, by creating extreme albinic con-
ditions in experiment and breeding from them. For the first set
of experiments the selection was made from numbers of copulating

Modification of Germinal Constitution of Organisms 239

pairs found in nature. The selected pairs were kept in separate cages,
as were their progeny, the only lumping of material being in the statis-
tical treatment of it. The great majority of such pairs and their off-
spring were not of any interest. Out of 311 pairs selected and mated
in the years 1896-1904, only 26, or 84 per cent of the total number of
pairs tried, were found capable of transmitting their particular varia-
tions. In many of these pairs it was certain that only one of the
beetles had the character in transmissible form, so that in 311 pairs,
or 622 individuals, the actual percentage of specimens showing heritable
variations was probably not far from 4 or 5 per cent.

Starting from a single pair of albinic individuals in which the selected
character was transmissible, and following the line of descent from
generation to generation, the fact is graphically shown in Fig. 77 that
the particular variation of the parent was not only preserved, but
carried close to the limit of normal variability of the species, and that
by selection the race was changed from one which was variable to one
which was relatively invariable-—that is, selection resulted in the pro-
duction of a race of albinic beetles of low variability, which, no doubt,
it would have been easy to maintain for a long period of time. From
the third generation a selection was made for the parents of the fourth of
the most and least albinic individuals, (A) still being the albinic race
and (B) the divergent race tending toward the opposite extreme. These
two lots of parents gave in the fourth generation two distinct polygons
which overlapped, only in the slightest extent. By continued selection
the polygons in the fifth generation did not overlap, and in this genera-
tion further division was made of (B) into (B) and (C). These two
lines were continued for several generations, diverging from the (A)
line, but not far nor rapidly. In the second generation there arose
two distinct groups separated by a wide gap (A) and (D), the latter
being the exact opposite of the (A) race. This (D) race was propa-
gated, and by selection produced the result shown in the polygons
along the line of descent (D), giving in the last generation of the race a
group of beetles of almost uniform condition. In all the lines of descent
(A), (B), (C), and (D), artificial selection did just what it was found to
do in the elements of coloration, namely, it created a race of low vari-
ability about the st.ndard chosen which it maintained as long as selec-
tion was practiced; but it did not carry the race beyond the normal

240 Heredity and Eugenics

*Normal"’ range of variation
A

mode:
5
B A
25) XI
, \\
= x
y 3 /
‘1 N
Aas Ix
[i
= VIII
\
2 \ VIL 9
=== MeBBEeF H
ras VI ;

;

bh -

Fic. 77.—Diagrammatic representation of the results obtained in the effort
to create albinic and melanic races by selection. Shows also the inability of quanti-
tative accumulations to carry the modification beyond the normal range of
variation, and also the rapidity with which races so created revert to the normal
standard when the selective influence is removed.

Modification of Germinal Constitution of Organisms 241

“ Normal" range of variation.
A

Mode. ae
pos
A
= XI
z =s|
Bp
j=
Ea :
t
=I IX
5 4
t
AA
=i VU
; vA
2 = VII
yz Z :
I 4 2
t ie E
& = u [8
ft tA
— # ay v
(z=
ui tA
|
= = 1 IV
a fd
|
2M
nr
we ;
BE eM
= 5 u
i= iw
| 2
y= A
RIE a | f
7

Fic. 78.—Diagrammatic representation of the results obtained in the creation
of races by selection of variations capable of transmission.

242 Heredity and Eugenics

range of variation of the species. That is, artificial selection can, as
DeVries points out, produce races and maintain them, but its power
to develop these races beyond the natural range of variability is yet
to be demonstrated.

From the series of cultures represented in Fig. 77, it is shown that
it is easy by selection to create races from a species, which would as
long as the artificial selection lasted, breed true to the ideal chosen.
Another such an experiment and two races breeding true that were
produced are represented in Fig. 78. From the parent generation two
selected groups, one melanic (B), the other albinic (A), were taken,
and from these, two clearly defined races without trace of intermediate
condition were produced. During each of eight consecutive genera-
tions slightly variable, light and dark races were maintained. At the
end of this time the material was divided and selection was stopped
in one group and continued in the other, but the lots were not allowed
to interbreed. The removal of the selective factor at once resulted in
a regressive shifting of the mode of each unselected race and in
increased variability, and this change continued through the eleventh
generation, when both unselected lots had moved back to the mode of
the species.

These experiments with color characters show very clearly that
artificial selection is with transmissible variations a powerful factor
and can greatly accentuate any character and maintain it in an
extreme condition, but that there are limits beyond which I was
not able to modify the characters by this agency. The experiments
also show that artificial selection works rapidly, and not, as has been
so often assumed, with extreme slowness. True, in experiment I
practiced a most rigorous selection, but not more rigorous than that
which the natural selectionists believe exists in nature.

The experimental production of general color variations and their
preservation by selective breeding give many points of interest. In
this I have confined my attention almost entirely to extreme light
and dark forms. To produce light forms I have used hot and dry
conditions, and for dark forms warm and moist. The experiments
herein recorded differ from those already given in that the entire life
of the beetles was passed in the conditions of the experiment, and
not the larval and pupal stages alone as in the experiments upon
coloration.

Modification of Germinal Constitution of Organisms

is)

4.

w

a , . .
"Normal Range of Variation”
a

BEES I
x S ‘2 y
ae HE Ba
ran f- r
N a if LN
{ ae, All \
1X NX 7 — =
| =
TIN if Ske
U7 BN y ae
Vill L wT]
; = nis
P- Win lia
| i t N | | i”
iN |
Vil H
a q_Wwe=
u Oo Viz =N a
| NY & * N a
VI i
a =
ai) ="
s N 7
| : 4
Vv ‘ 3
==
= man may
rn Prt Tirey
4 | +]
IV 2 A
t J C =
D
'l4
"4
14 A
AF
Pp
L

Classes 23222120 19 IS 716 ISM IZ IZNIOIBTES4Z2tabeodef gh.

Fic. 79.—Diagrammatic representation of the results obtained in the creation
of albinic and melanic races by the combined influence of selection and environ-
mental stimuli. These experiments show a difference from the results shown in
some of the former diagrams, in that there are a number of extreme variations
produced which apparently are stable in several successive generations; however,
when the selective effect is removed the divergent race is seen not to be stable and
to revert with considerable rapidity to the mediocre or parental stock.

244 Heredity and Eugenics

In Tig. 79 are brought together in diagrammatic form the data
and general history of cultures where both light and dark forms were
produced and further subjected to experiment. The black polygons
represent the selected groups of parents, the ruled polygons, the
offspring. The appearance of “mutants” beyond the normal range
of variability is indicated by the small white polygons. .... The
series 1s a complex one, involving processes other than artificial
selection and introducing factors of interest which are the key to
further experimental study. At present only that portion directly
concerned with selection or selective processes need be considered.

In the first, or parent, generation I selected 6 copulating pairs of
beetles from the hibernating population, and kept them and their
progeny in natural conditions. From the 6 pairs were obtained in
the second generation 1,320 mature beetles, and from these, two
groups of copulating pairs of to each (A and B) were selected and
reared in the third generation, but showed no modifications as the
result of selection. These hibernated, and selections from each lot
were reared in the fourth generation, but showed no modification.
I now felt sure that the material was pure, that is, normal, and carried
no tendencies to appear in divergent extreme variations. Accord-
ingly, from the two series selection was made of as nearly modal
individuals as possible, and the two selected lots were mixed and
divided into two lots of 10 pairs each (C) and (D). These were
placed, as soon as possible after emerging, in surroundings produc-
tive of dark and light conditions of coloration, and allowed to breed,
producing in the fifth generation two distinct lots of descendants,
one light, the other dark. These hibernated, and after emerging
in the following spring were allowed to breed, when it was found that
out of 50 mated pairs 31, or 62 per cent, were able to transmit their
particular variations in full strength, a huge increase over that
found in selections from nature. From each group 5 pairs were
selected as the parents of the sixth generation. These gave, as was
expected, distinct lots of individuals more melanic and more albinic
than their parents, and each also produced individuals differing in
many respects from the parent stock, and beyond the usual range of
variability. In the five following generations the same thing was
repeated, as may be seen from Fig. 79; that is, from each group of

Modification of Germinal Constitution of Organisms 245

selected parents there came a general population less and less variable,
and a greater or less number of highly divergent forms beyond the
normal range of variability of the species. These latter we shall
consider in another place.

In this series of cultures a normal parent stock has been subjected
to artificial selection aided by powerful environmental stimuli, both
having the production of the same end in view. The results, however,
were a keen disappointment; the inability to produce by selection and
powerful environmental influences a race much beyond the normal
limits of variability of the species might easily be taken to indicate
the impotency of selection. The ease with which the beetles moved
back toward the mode when selection was no longer practiced and
the conditions of existence became modal, when joined to the data
of place and geographical variations, allows only of the conclusion
that while differently colored races and modifications of this organ-
ism occur in nature and are produced in experiment by artificial
selective processes and local environmental influences, such modi-
fications are limited by the natural limits of variation of the species
and persist only as long as the maintaining processes are present
and are utterly incapable of existence under adverse conditions,
reverting to the species type. That is, artificial selections or local
influences are able to modify, and to a certain extent create, races
founded upon those variations which are ordinarily killed off by
natural selection; but in the creation of such races we really have
two forces—a species tendency and a local (or artificial in experiment)
—acting against one another, with the result that selective divergence
to a certain limit is attained, but beyond that the racial divergence is
slow or entirely stopped. When the local or artificial selection is re-
moved the species selective tendency causes a regression to the type
of the species. It may be objected that my experiments do not cover
a sufficiently long series of generations to have accomplished the
result intended, and this may be true; but selection is a powerful
formative factor and works rapidly up to a certain limit, and this has
been abundantly proven by plant and animal breeding for fifty years.
Why should it not also be able to establish a race on permanent
footing with the same rapidity? It is known from the rearing of
domestic animals and plants that constant selection is necessary

246 Heredity and Eugenics

to maintain the race. In so far as color characters are concerned,
by artificial selection we can easily produce and maintain a race, but
cannot establish it as an independent one; it is possible to create
isolated races from extreme variations, and by selection keep them
isolated, but it seems very difficult to permanently establish them.
On the whole, selection would appear as a relatively impotent factor
in evolution. Two points should be noted, in passing, namely, the
number of highly divergent variations beyond the normal range of
fluctuating variation produced in this last series of experiments, and
the increased percentage of individuals which show variations capable
of being transmitted to the progeny.

It seems to be a well-established fact that by quanti-
tative accumulation, pigment or any other character in the
organism can be made to diverge rapidly up to a certain
limit, beyond which it is practically impossible to go. More
striking, however, is the rapidity with which such races
revert to the modal condition of the parent stock when
the selective process has ceased. This phenomenon has
been characterized as regression toward the mean, and
it may represent either one of two processes—an inherent
tendency in the organism to revert to the standard, or it
may represent a selective process which goes on within the
organism. Iam of the opinion that the latter is the correct
explanation of this, for the following reason: modification
by the quantitative accumulation of minute fluctuating
variations is always working against what may be termed
the natural selective tendency, that is, against those tend-
encies which surround every organism and which eliminate
extremes in each generation through one cause or another,
allowing the modal type to persist. Any effort, therefore,
to preserve the extreme type comes in conflict with that
which serves to eliminate extremes and preserve the modal
type. There are two conflicting forces, one which tends

Modification of Germinal Constitution of Organisms 247

to preserve the extreme and by rigorous selection to eliminate
the mean, and the other which tends to eliminate the
extreme and preserve the mean. Rigorous artificial selec-
tion makes the preservation of the extreme the more potent
of the two, and results in rapid divergence, but not in
unlimited divergence, and when this selective process ceases
the natural selective process again becomes operative with
the result that there is rapid regression to the mean racial
standard.

Confusion exists in many records of selection experi-
ments, due to the presence of biotypes or phenotypes, so
that the selection is really a process of separating the present
elemental forms. In the above-cited experiments only one
biotype was present and this was not capable of being
changed by selection—quantitative—beyond the normal
range. The bearing and necessity of working with one
biotype in this selection work and not with a complex of
several is well known to all students of genetics at the present
day, although not adequately appreciated by practical
breeders.

The facts concerning inconstancy and reversion are well
known to breeders of animals and plants, who must practice
constant selection to maintain the standard of their artifi-
cially improved races. Is it possible to produce, byaselective
process, modifications which are permanent and which do
not revert on the cessation of the selective action, which
maintain themselves when brought in contact with the
parent species, and which maintain themselves when placed
in nature? In selective processes of this kind, amount
is a negligible quantity; only pattern arrangement need be
considered. In other words, those differences in the consti-
tution of the organism which localize specific characters

248 Heredity and Eugenics

in definite areas can be acted upon by selective combinations
to produce permanent results. One example will serve to
illustrate this.

Material of L. signaticollis Stal, a specific form limited
to a narrow habitat in nature, and of low variability in all
of its characters, was the basis of this experiment in selec-
tion. Compared with other members of the genus with
which it is closely related, the variations of L. signaticollis
are trivial, so that one would on a-priori grounds be certain
to regard it as a hopeless task to attempt with L. signati-
collis studies in experimental evolution by selective methods.
By a process of combining variations in the pattern of the
pronotum it is possible through a series of generations to
create a type of pattern permanent in all respects, and which
behaves, when crossed with other patterns, with ali the
sharp alternativeness of characters found in nature.

The selection was begun in the ninth generation of the
stock which had been bred as group cultures and as pedigree
cultures and had never shown the modifications which
were produced; further, the modifications produced are
not known to exist in nature. Im the F, generation, a
combination was made of the pronotal pattern, and from this
there arose a variable progeny, F,,.. From generation F,,,
matings were made and during generations F,,, F,,, F,,,
F,,, F,,, and F,., etc., the combinations were made from
generation to generation, with the end result that there
has been developed a permanent strain, which since the
F,, of F,, generation has.remained stable. In this strain
the spots are all fused into one solid mass and are carried
backward until they completely border the posterior edge
of the pronotum, and anteriorly to the anterior edge and
laterally, leaving only a small border unpigmented. Such a

Modification of Germinal Constitution of Organisms 249

combination is not known in nature, but there has twice
appeared in my cultures a somewhat similar variation which
could be classed as a sport, which variations, however
always failed to perpetuate themselves.

These cultures are able to maintain themselves under the
conditions of the vivarium in both group and _ pedigree
cultures without further attention, or attempts to main-
tain the race. More interesting, however, is the behavior
of these modified forms when placed in nature in their
normal habitat, where they have maintained themselves
with undiminished attributes, and there has not been the
slightest indication of reverting to the ancestral state.
When material of this type is crossed with material of the
parental stock obtained from the original locality, the
modified attribute behaves as a striking dominant alternative
characteristic.

Of further interest is the ontogenetic series of events in
the development of this modified color pattern. In this
instance I know step by step exactly what went into the
combination, also what the ontogenetic sequence of events
was in each type of parent, and it is naturally expected that
the modifications would present a series of ontogenetic
stages one following the other, and that the ontogeny of
these modified individuals should rather closely recapitulate
the recent events which the organism has gone through in
attaining its present state. This is exactly what the organ-
ism does not do. Like any well-regulated physico-chemical
mechanism it cuts out the non-essential and takes the short-
est cut to attain its present end. This short cut, wherein
stages which it passes through in its phylogenetic develop-
ment are left out, and where many characters are lost com-
pletely, shows that in this instance a modified pattern has

250 Heredity and Eugenics

arisen by an accumulative process, giving all the same
permanence and strength of character as is found in what
are called natural species or characters.

The same process has been applied to other forms and
attributes with identical results, the only limitations being
such as are imposed by the physical constitution of the
organism itself, or of the part in which the modification is
being carried on, so that a character might become after a
time decidedly injurious in the economy of the species and
therefore come under the operation of natural elimination.
This pattern, however, is a neutral character and the only
limitation is that imposed by the physical constitution of
the part and there is apparently no direction in which the
modification must never go.

In another series derived from the original stock, modifi-
cations were carried out in the reverse of this one, producing
a stock in which all of the spots were reduced to round simple
areas with absolutely no tendency to fusion or breaking up
of the spots into many tributary rows. From these experi-
ments two points are clearly demonstrated: First, it is
shown that a selective process may permanently modify
one of the most inflexible of characters, namely, pattern,
and this modification may even greatly exceed any of the
variations known in the species. This selective process is
different from the quantitative accumulation which has
been employed by plant and animal breeders. It is not a
process of hybridization, but is analogous to the processes
which a chemist would use in synthetizing a complex com-
pound, adding to it first one thing, then another, subtracting
from this a product, then adding to it some more, until the
end product is totally different from the original material.
It is a process of synthesis and not of accumulation.

Modification of Germinal Constitution of Organisms — 251

The second observation has a bearing upon the current
theories of biogenesis and orthogenesis, showing the distinct
failure of this modified organism to repeat in its ontogeny
the stages which it has recently passed through in its
phylogenetic development. It has long been maintained,
from a paleontological standpoint, and from study of the
ontogeny of an organism, that the stages passed through
represent a recapitulation of the more essential stages of its
recent development. Jackson on paleozoic echini, Hyatt
on ammonites, and Beecher on brachiopods have shown
that there is a constant dropping of the earlier and more
primitive stages in the ontogeny of a species, and a reduc-
tion of the later stages. There is of course a large amount
of permanent truth in the view obtained from these paleon-
tological studies, that the organism recapitulates its phylo-
geny, at least to a greater or less extent, but it is equally
true that the literal interpretation of this—the utilization
of the ontogenetic stages as a test in determining relation-
ships and direction of evolution—is futile.

It would be difficult to interpret a case like the one
given on any other basis than that used—that the conditions
found represent the best adjustment which the physico-
chemical mechanism could possibly achieve in order to
attain a definite end. To do this, instead of following an
irregular and complex path, it cuts straight across, elimi-
nating minor steps which have played a phylogenetic réle
but have no part in the achievement of the final end result
in the ontogeny of the parent stock.

It has been maintained that evolution is irreversible
and that once started it must continue to the end. It is
difficult to conceive of any reason why this should be so
unless there be assumed the existence of an inherent force

to

Heredity and Eugenics

to
Un

or cause driving organisms toward a series of goals, which,
when passed, represent the final goal of that particular race.
If this conception were true, then there would exist in
organisms a state totally unlike that found elsewhere in
nature. In no physical or chemical phenomena does any
such condition exist, but rather, an array of substances
which can be combined and recombined in an almost infinite
series of combinations, which can be built up to complex
aggregations and with equal facility reduced down to the
atomic groups from which they came. In other words,
by a selective synthetic process it is possible to create or
synthetize, and likewise, by a selective analytical process
to analyze, and the irreversibility of evolution exists only
in the dogmatism of some essayists, and not in the
materials of nature.

To what extent the selective process is operative in the
production of variation in nature is unknown. It is not
probable that in nature there would exist the arrangement
of variations which I brought about in experiment, but in
nature I should rather look for a very decidedly haphazard
process, bringing about chance combinations which would
produce this or that result, and these chance combinations
might any two of them combine and produce a third chance
combination which would stand apart from the parent
species—the product of the two others, but if found in
nature it would be described as a ‘‘mutation.”” What rdéle
these variations, and I am convinced that they are potent
factors in evolution, really would have in the general evolu-
tion of organisms and in the development of species, is un-
known. It is not inconceivable that a variation might
thus arise which, behaving as a strong dominant or as a
dominant heterozygote, could increase in numbers and

Modification of Germinal Constitution of Organisms — 253

after a time replace the parent species to a considerable
extent, if not completely.

C. Discussion—Summary

Probably no question in biology has received more
attention, and certainly few are so little understood, as the
method whereby those variations which are productive of
permanent change arise and become incorporated into the
germinal constitution of the race. If the possibility of
variations arising in a manner like that assumed in the
neo-Lamarckian conception be admitted, it must also be
admitted that there is at present no critical evidence of any
such method of origin. As far as experience warrants a
conclusion, there is at present no escape from the general
proposition that all variations that are productive of per-
manent germinal changes, arise primarily in the germ and
appear secondarily in the soma. It must be understood
that by this proposition it is not asserted that it is the only
possible conception, but that it is the only one concerning
which there is at the present time any definite proof.

Knowledge concerning the germ cells, which are the
germ plasm or else the carriers of it, is largely anatomical in
character, derived from studies in cytology and in the main
is one sided, incomplete, and has been too much directed to
the study of the chromosomes. That this is the condition
is not strange when one considers the wonderful regularity
with which the chromosomes are divided between the
daughter cells, and the precision and regularity of the process
immediately preceding and accompanying fertilization.
These phenomena, so fundamental and common to all
organisms, have impressed biologists profoundly and very
naturally the opinion arose that the chromosomes were the

254 Heredity and Eugenics

bearers of that which conditions the characteristics of the
subsequent generation. Recent cytological studies, how-
ever, have demonstrated that the early conception of
equality in the distribution of the chromosomes is not
entirely true, but that there is a regular and unequal dis-
tribution of the chromosomes which occurs in many, if
not all animals, producing in some two classes of ova, in
other instances two classes of spermatozoa.

These chromosomal differences in some unknown manner
are now generally admitted to be associated with the
determination of sex; hence the “accessory chromosomes”’
which go to make chromosomal differences in the germ
cells are regarded by some as sex determinants. That they
are sex determinants in the sense in which ‘‘determined”’
has been used is not proven. The results obtained by
Morgan in Phylloxera seem crucial and show that the extra
chromosomes are an accompaniment of differentiation, and
not the cause thereof. At any rate it is definitely proven
that the existence of the accessory chromosomes represents
a definite difference in the qualities and constitution of the
germ cells, and thus gives in gametogenesis germ cells
differing from one another by sharp alternative differences.
There is no a-priori reason why the same may not be true of
attributes and qualities in the germ cell which are not
capable of observation by present cytological methods.

In the last decade the work of many investigators, but
especially that of Conklin, Lillie, Morgan, Driesch, and
Wilson, has shown that the germ cells are in reality highly
complex structurally, possessing a definite organization
and polarity, with a distribution of various elaborated sub-
stances which are individually more or less necessary to the
proper development of particular parts of the future embryo.

Modification of Germinal Constitution of Organisms — 255

It is clearly shown that in the germ cell before fertilization
there is a fundamental symmetry, polarity, from which there
arise during ontogeny the symmetries and arrangements
existing in the developing individual. This symmetry,
as far as there is any evidence, continues back through all
the cell generations which arise during gametogenesis,
and on the basis of what is known of development in the
germ cell, it seems to be a symmetry directly derived from
the parent zygote. In other words, in the continuity of
the germ cells from generation to generation, there is a
continuity of the symmetries and physical constitution
characteristic of the germinal material, a continuity of
germinal organization. It seems clearly established, espe-
cially by the work of Lillie and Morgan, that there is a
fundamental background, or matrix, in the germ cell in
which the original symmetries are expressed. For the pres-
ent the entire germ cell must be regarded as the germinal
material or germ plasm, and our problem in the investiga-
tion of the origin of germinal variations is to discover
by what methods changes in the germ cells are brought
about. This is one of the most difficult problems con-
fronting biologists, and one which is possibly incapable of
solution, at least in the near future, and perhaps may
forever remain unsolved.

The chemical changes which go on in the living sub-
stance, especially those which follow in the metabolism of
organisms, have been roughly outlined, but these metabolic
processes, while they may result in the elaboration of pro-
ducts to be incorporated into or removed from the organism
in one way or another, do not possess any capacity for
carrying on their operations excepting in the living mass.
Moreover, we understand in a broad way the mechanical

256 Heredity and Eugenics

and physical principles involved in the passage of fluids
from one part to another or to the outside, and something
of the réle which katalytic changes play in organic activi-
ties. The time has not come when this information can be
directly applied to the problem of the chemical nature of
germinal changes.

As regards form and pattern, the biologist is confronted
in organisms with the same difficulties as are presented to the
physicist and chemist to explain form and pattern in non-
living substances. No physicist would presume to say what
it isin the composition of a crystal which makes so definitely
for a specific form of face, hardness, and optical properties.
The problem is the same in both living and non-living
substance, and the forces which determine form and pattern
seem to be properties of the entire mass and are not local-
ized, and are probably produced in organisms, as in non-
living masses, by the sum total of the interactivities of
the mass at the moment of observation.

In every part of the organism there is a symmetry which
is the outgrowth of the original symmetry from which the
organism developed. Variations in the secondary or later
symmetries may be large, but almost never are there
variations in the fundamental symmetries which distinguish
phyla. Evolution is mainly concerned in the problem of
the formation of species or attributes with variations in
these secondary symmetries and patterns. I have shown
how certain of these symmetries may be modified.

Not the slightest clue of what it is that is modified in the
germ cells of a particular species as the result of any modi-
fying process has been recorded, and the usual attempted
explanations are based upon assumed a-priori conceptions,
usually atomistic in character, on the order of Darwin’s

Modification of Germinal Constitution of Organisms 257

provisional hypothesis of pangenesis, the id-determinant-
biophore fabric of Weismann, or the pangene complex of
DeVries. Much has been written concerning the uselessness
of such conceptions as explanations; much has been
written in their favor, and the only truthful statement
possible is that there is no evidence for their existence.
The important contribution is the experimental evidence
showing that the symmetries and patterns in organisms are
definitely modifiable as the result of synthetic and other
processes which may be carried on under observation, and
which achieve definite results. In most instances thus far
recorded results are achieved rapidly, and the end is not
postponed or approached in a halting, zigzag manner, but
the modification is in appearance definite, precise, reminding
one of the regular and precise operations seen in chemical
and physical processes.

There is an interesting analogy between the processes
which may be carried on in organisms in modifying the
symmetries by combining definite characters, and those
which may be carried on in crystallography, as for example,
where certain impurities may be introduced into the crystal-
lized form and may definitely alter the attributes of the
crystal, such as shape, color, hardness, specific gravity,
etc. That the parallel is an exact one there is no evidence,
but it is at least suggestive in that both the results occur
with sharp alternativeness which is so characteristic of
chemical and physical operations.

It does not seem probable that germinal modifications
in form and symmetry arise through the changes in particu-
lar chemical constituents within the germ cell, as, for
example, a particular katalytic agent, or the rearrangement
of the side chains in some complex molecule, because, as far

258 Heredity and Eugenics

as is known, these are superficial relations and are not of
themselves concerned in establishing the fundamental
symmetries and activities which seem to be in the main
conditioned and controlled by the colloidal matrix which
underlies all visible structure. The only safe statement which
can be made at present is an acknowledgment of our ignor-
ance of what the changes are in the germ cell which are
productive of new arrangements in form and symmetry.
However, it is experimentally proven these fundamental
relations can be altered by one process or another, thus
giving methods of inducing changes and of discovering
what changes are possible, both as regards the limits of
change, direction, rate, etc., and this knowledge may be
of great practical value even though the underlying physico-
chemical operations are still undetermined and _ possibly
unknowable.

In the modification of characteristics which are directly
conditioned by chemical activities, as, for example, color,
there seems a greater possibility of attaining at least a
general idea of the processes involved in the germ cells in
producing permanent changes. Pigments, throughout the
organic world, are pretty generally the result of metabolic
processes and are probably in most instances the result of
the oxidation of various cleavage products which have
themselves been formed by the breaking down of more com-
plex substances within the cell. Many of these chromogen
substances are possibly waste materials in the organism,
which perhaps could not be further utilized in the economy
of the animal, so this method arose of converting them into
more or less harmless substances and depositing them in
places where they would be least inconvenient to the
organism. This old conception of the character of coloration

Modification of Germinal Constitution of Organisms 259

meets with little favor today, because there is too much
good evidence to show that even under adverse conditions
the development of pigment takes place, where the organism
expends in developing the pigment, material, and energy
which it needs to carry on activities vital to its existence.
The pigment substances which develop in connection with
pathological growths and the development of pigment even
in the face of starvation are all indicative of the deep-seated
nature of pigment formation in organisms.

The capacity to produce a given pigment is as firmly
a part of the germinal constitution as are structural char-
acters, which, by some at least, are regarded as the only
attributes worth considering. It is well known that in all
organisms there is in nearly all cells at least the possibility
of producing from the ordinary breaking down of the sub-
stance of the cell, materials which can serve as the chromogen
base for the elaboration of various kinds of pigment, but
this aspect of the subject has been considered in an earlier
part of this paper.

The question in the production of germinal modifications
of the pigment-forming capacity in organisms is, what is
it in the germ cell that is modified? There is little to
warrant an assumption that these phenomena are based upon
representative particles or upon individualized entities of
any sort, and I doubt if many investigators really attribute
to pangenes and biophores the capacity and importance
which some writers who are antagonists to the method of
expression seem called upon to believe.

Perhaps the best evidence in this direction is that
derived from the studies in inheritance by the Mendelians.
Their treatment of the subject of color inheritance has
shown clearly that there is something in alternative char-

260 Heredity and Eugenics

acters which, when a definite array of conditions are brought
together, produce a definite color, and when another array
is brought together a different color results, or perhaps
no color.

At the present time there is no evidence that in the cells
there is incapacity for the production of pigment, or inca-
pacity for the production of either chromogen or enzyme.
The only evidence is that the pigment does or does not
appear when germ cells derived from parents of a certain
character are combined. In the minds of some it follows
from this that something is lacking in the way of a specific
activity; in the minds of others it is due to the fact that a
sufficient quantity of one or the other of two necessary
substances is not present. Still another explanation is
that there is lacking strength or energy to produce the one
or the other.

Further, the situation can be explained by adopting the
idea of inhibitors, activators, etc., which would inhibit the
appearance of pigment in one case, and then, by the inhibi-
tion of the inhibitor permit the appearance of pigment in
another case. Much fine evidence exists from the work
of the neo-Mendelian hybridologists that factors, deter-
miners, accelerators, and inhibitors exist and can be sub-
jected to experimental tests; however, to attempt to
explain observed conditions by asserting that the organism
is incapable of producing the requisite amount of chromogen
or activator is really no explanation, because it is well known
that a minimum amount of activator may convert an almost
unlimited amount of chromogen into a color-forming sub-
stance, provided the substance produced as a result of the
katalyzing process is removed with sufficient rapidity so as
not to impede the process. This is a well-known principle

Modification of Germinal Constitution of Organisms 261

in all katalytic action. It does not seem a plausible expla-
nation of germinal color variation to attempt to place it
upon a quantitative basis, in view of the well-known facts
of katalysis. Likewise, explanation of the situation as being
due to varying germinal strength, energy units, energy, etc.,
does not aid, and only confuses a situation already suffi-
ciently confusing. If by strength is meant strength of
katalyzer, there again a weak agent may produce a relatively
large result if advantageously placed and given a sufficiently
long time in which to act to bring about a definite result, and
a relatively weak agent may, under advantageous condi-
tions, convert a relatively enormous amount of chromogen
into pigment-forming substance. It would be of interest to
know the chemical constitution of some of the attributes;
in the case of albino animals, for example, is the chromogen
present, and is the oxidizing agent absent or vice versa ?
It seems improbable that the oxidizing enzymes should be
entirely lacking, and it may be true that there is a specificity
in these enzymes, as has been suggested by various authors,
and a specific enzyme might well be absent, and in its
absence there would be no production of color.

As far as I am able to get at the processes involved in
the production of color variations by means of incident
physical and chemical factors, it seems that the change is
one which involves the entire mechanism of the cell, and
is not resident in any particular part thereof. By experi-
mental means I have produced a modified condition of
coloration, and in this the interactions of chromogen and
katalyzer are conditioned in their appearance and inter-
action during ontogeny by the mass in which they are, and
are entirely dependent upon the capacity of the mass to
retard, accelerate, or extend the rate and time of action,

262 Heredity and Eugenics

or to remove the by-products which would inhibit the
katalyzing action which would normally go on. Under
the modified conditions there may be produced no greater
alteration in the germ than a reversed action of some
enzyme, and although the same enzyme may be present,
its reversed action is such that the pigment-forming sub-
stance is not formed, but its activity is directed to other
activities than to building pigment-forming substances.
The same enzyme may again be reversed in its direction
either by combining with some other substance, or by being
acted upon by some incident force, and this reversal of action
in the enzyme may therefore produce the formation of
color substances. It does not of necessity follow that the
changes induced are at all concerned with the substances
which actually themselves form the pigment. For example,
in germinal modifications which have been produced, where
the color is diminished in intensity, there may be identical
amounts of chromogen and enzyme, but the changes may be
due to changes in other factors which are necessary to the
color formation by removing from the field of operation
certain inhibiting by-products.

It is possible that a profitable point of attack upon these
problems lies in this direction. The chief difficulty, however,
is the small size of most germ cells, and in those of large
size the existence in the egg of a large amount of stored
food supply effectually inhibits investigation. It is prob-
able that for the present, interpretation of the process of
germinal change must be more by analogy than by actual
physical and chemical analysis.

In the experimental production of modifications of the
germ plasm two definite ideas as to the nature of the change
have been expressed. MacDougal is of the opinion that

Modification of Germinal Constitution of Organisms 263

in many of his derivatives all of the attributes of the organ-
ism were modified each more or less independently of the
others. I have expressed the opinion that, as far as my
observations go, one character is in the main most modified,
and then a greater or less array of lesser characters are less
modified in correlation. There is at once a fundamental
difference between these two expressions of experience, a
difference which may be due to the difference between plants
and animals, but I do not understand how all the attributes
of an organism can be modified at one time by incident forces.
MacDougal says, “The induced forms in plants show many
new qualities of fairly equal importance as far as such things
may be estimated, and these might be independent of each
other.”

I do not, at least in animals, feel competent to determine
the equality of characters, and thus far I have never seen
examples, where any considerable array of characters were
modified equally. As a matter of fact, I have no basis
in experience which would enable me to decide whether
characters were modified equally or not.

If one accepts a particulate conception of the constitu-
tion of an organism as a true expression of organic con-
stitution, the modifiability of characters as expressed by
MacDougal would be the natural result. I have thus far
seen no evidence of such a condition, at least in the materials
under my observation, and I am therefore compelled to
regard the organism as a whole in the sense that it represents
a state of stability which is achieved and retained by a
mass of matter under a given set of conditions. The com-
bined elements are not independent and do not exist in the
organism as individualities, but as component parts of the
whole, as long as they comprise a part of that particular

264 Heredity and Eugenics

substance, even though they are capable of unlimited meta-
thetic change in heredity.

There is another point upon which MacDougal and I
differ. MacDougal says, that “his new plants do not
hybridize freely, if at all, even when grown with branches
interlocking with the parental type,” which differs from the
conditions which I have found, where intercrossing occurs
freely with the parent species. Comparison is difficult
between organisms so widely separated as those used by
MacDougal and myself, and it is entirely possible that the
results of particular processes may result differently in
different organisms.

The results obtained by Gager through the use of radium
upon different plants, the modifications of Sempervivum by
Klebs, the changes in yeasts and bacteria, etc., can hardly
be incorporated at the present time in this discussion in
that they have not been carried far enough. Gager’s
opinion that the inheritable results obtained by him were
possibly due to a disturbance in the chromosome complex,
is simply an explanation based upon an old morphological
conception. It has not yet been shown that specific chromo-
somes are endowed with specific characters resident in
them, and until that point is decided definitely the explana-
tion of germinal variations on the basis of chromosome
behavior must stand aside.

In animals the experiments of Kammerer, Pshibram,
Woltereck, Morgan, and the older experiments of Fischer,
Standfuss, Weismann, and others, do not furnish data for
a discussion of and far less for a solution of the problem.
However, an important point is established by all of these
investigations which show uniformly that the germ cells are
most susceptible to the influences that produce germinal

Modification of Germinal Constitution of Organisms 265

changes immediately before and during maturation. This
period is known to be a critical one in the life of the germ cell,
and is a time when many processes are in progress, and when
there exists a delicate balance susceptible of being per-
manently upset. There is evidence in some of my experi-
ments to show that earlier periods in the life-history of the
egg are susceptible to stimuli and produce at these earlier
periods more profound modifications than are produced
later, but are more difficult to induce. During the growth
period there is a constantly increasing elaboration of poten-
tialities, with an increasing array of substances and sym-
metries, and a slight change in this primary constitution
might result in large end results.

It is evident that the problem of germinal change is one
of difficulty, and involves more of indirect than of direct
methods of investigation. There is little reason to expect
that present biochemical methods can give a solution, but
they may give valuable suggestions for further indirect
investigation. It seems not improbable, however, that
this problem, like so many others in biology, must await the
solution of the larger question of what life is before it will
be possible to express in exact terms the nature of germinal
changes. Our present status, with several methods of pro-
duction and much knowledge of the behavior of induced
germinal changes available, is a basis from which great
advances in knowledge and in operation may reasonably be
expected.

CHARLES BENEDICT DAVENPORT

Station of Experimental Evolution, Carnegie Institution of
Washington

CHAPTER VIII

THE INHERITANCE OF PHYSICAL AND MENTAL TRAITS
OF MAN AND THEIR APPLICATION TO EUGENICS

The general laws of heredity have already been fully
explained. But every person has a different way of express-
ing them and a little repetition will do no harm; and so,
very briefly, I will recapitulate the principles of heredity.

First of all, we find useful the principle of the unit-
character. Whether it be ultimately accepted or discarded,
it is useful today, and so we accept it as a guiding hypothesis.
According to this principle characters are, for the most part,
inherited independently of each other, and each trait is
inherited as a unit or may be broken up into characters
that are so inherited.

Next it must be recognized that characters, as such, are
not inherited. Strictly, my son has not my nose, because
I still have it; what was transmitted was something that
determined the shape of his nose, and that is called in
brief a ““determiner.’”’ So the second principle is that unit-
characters are inherited through determiners in the germ
cells.

And finally, it is recognized that there really is no inherit-
ance from parent to child, but that parent and child
resemble each other because they are derived from the
same germ plasm, they are chips from the same old block;
and the son is the half-brother to his father, by another
mother.

These three principles are the three cornerstones of
heredity as we know it today, the principles of the inde-

260

270 Heredity and Eugenics

pendent unit-characters each derived from a determiner
in the germ plasm.

It is my agreeable task to show in how far the known
facts of heredity in man are in accord with these principles.
I may say at the outset that I have no doubt that all human
traits are inherited in accordance with these principles;
but knowledge proceeds slowly in this field.

As a first illustration I may take the case of human eye
color. The iris is made up of a trestle work of fibers, in
which are suspended particles that give the blue color.
In addition, in many eyes, much brown pigment is formed
which may be small in amount and gathered around the
pupil, or so extensive as to suffuse the entire iris and make
it all brown. It is seen, then, that the brown iris is formed
by something additional to the blue. And brown iris may
be spoken of as a positive character, depending on a deter-
miner for brown pigment; and blue as a negative character,
depending on the absence of the determiner for brown.

Now when both parents have brown eyes and come
from an ancestry with brown eyes, it is probable that all
of their germ cells contain the determiner for brown iris
pigmentation. So when these germ cells, both carrying
the determiner, unite, all of the progeny will receive the
determiner from both sides of the house; consequently the
determiners are double in their bodies and the resulting iris
pigmentation may be said to be duplex. When a character
is duplex in an individual that means that when the germ
cells ripen in the body of that individual each contains a
determiner. So that individual is capable, so far as he is con-
cerned, of transmitting his trait in undiminished intensity.

If a parent has pure blue eyes, that is evidence that in
neither of the united germ cells from which he arose was

Inheritance of Physical and Mental Traits 271

there a determiner for iris pigmentation; consequently in
respect to brown iris pigmentation such a person may be
said to be nulliplex. If now such a person marry an indi-
vidual duplex in eye color, in whom all of the germ cells
contain the determiner, each child will receive the deter-
miner for iris pigmentation from one side of the house only.
This determiner will, of course, induce pigmentation, but
the pigmentation is simplex, being induced by one deter-
miner only. Consequently, the pigmentation is apt to be
weak. When a person whose pigment determiners have
come from one side of the house forms germ cells, half
will have and half will lack the determiner. If such a
person marry a consort all of whose germ cells contain the
determiner for iris pigmentation, all of the children will, of
course, receive the iris pigmentation, but in half it will be
duplex and in the other half it will be simplex. If the two
parents both be simplex, so that, in each, half of the germ
cells possess and half lack the determiner in the union of
germ cells, there are four events that are equally apt to
occur: (1) an egg with the determiner unites with a sperm
with the determiner; (2) an egg with the determiner unites
with a sperm without the determiner; (3) an egg without
the determiner unites a sperm with the determiner; (4) an
egg without the determiner unites with a sperm without the
determiner. Thus the character is duplex in one case,
simplex in two cases, and nulliplex in one case; that is, one
in four will have no brown pigment, or will be blue eyed.
If one parent be simplex, so that the germ cells are equally
with and without the determiner, while the other be nulli-
plex, then half of the children will be simplex and half
nulliplex in eye pigment. Finally, if both parents be nulli-
plex in eye pigmentation (that is, blue eyed), then none of

272 Heredity and Eugenics

their germ cells will have the determiner, and all children
will be nulliplex, or blue eyed. I have gone into the inherit-
ance of eye color at some length because it serves as a
paradigm of the method of inheritance of any unit-character.

Let us now consider some of the physical traits of man
that follow the same law as brown eye color, traits that are
clearly positive, and due to a definite determiner in the
germ plasm. And first, I may refer to hair color.

Hair color is due either to a golden-brown pigment that
looks black in masses, or else to a red pigment. The
lighter tints differ from the darker by the absence of some
pigment granules. If neither parent has the capacity of
producing a large quantity of pigment granules in the hair,
the children cannot have that capacity, that is, two flaxen-
haired parents have only flaxen-haired children. But a
dark-haired parent may be either simplex or duplex; and
so two such parents may produce children with light hair;
but not more than one out of four. In general, the hair
color of the children tends not to be darker than that of
the darker parent. Skin pigment follows a similar rule.
It is really one of the surprises of modern studies that
skin pigment should be found to follow the ordinary law
of heredity; it was commonly thought to blend. In
crosses between Negroes and Caucasians, such a blend was
stated to occur, and it was believed to be permanent, so
long as the hybrids were mated together. Actually, the
method of inheritance is like that of hair pigment, the
skin color of the children rarely much exceeds that of the
darker parent. There are stories of two white parents
having black-skinned children, and if these are true they
constitute striking exceptions to the general rule. The
inheritance of skin color is not dependent on race; two

Inheritance of Physical and Mental Traits 273

blondes never have brunette offspring, but brunettes may
have blondes. The extreme case is that of albinos with no
pigment in skin, hair, andiris. Two albinos have only albino
children, but albinos may come from two pigmented parents.

Similarly, straight-haired parents lack curliness, and
two such have only straight-haired children. Also two
tall parents have only tall children. Shortness is the trait:
tallness is a negative character. Also when both parents
lack stoutness (are slender), all children tend to lack it.

ne

ce
eee N OO &©O
ORONOORNNHON

Fic. 80.—Inheritance of monilithrix—a positive character. Black symbols
represent affected individuals.—ANDERSON.

We may now consider briefly the inheritance of certain
pathological or abnormal states, to see in how far the fore-
going principles hold for them also. We shall find that
sometimes the abnormal condition is positive, due to a new
trait; but sometimes, on the contrary, the normal condi-
tion is the positive one and the trait is due to a defect.

Among conditions due to a new determiner may be men-
tioned a beaded peculiarity in the form of the hair, called
monilithrix. Affected persons tend to have affected off-
spring (Fig. 80). Two unaffected parents do not ordinarily

274 Heredity and Eugenics

have affected children (in the illustrative case nothing is
known about one of the two parents). When one parent
only is affected about half of the children are affected, since
each affected person is simplex.

Again, some family strains exhibit imperfection of hair
or even baldness associated with imperfect nails (Fig. 81).
Here there seems to be a determiner that stops the develop-
ment of these organs of the skin. Normal persons are with-
out this determiner and so cannot have affected children.

O)®@

on @O © “ii 6 0

Se aRe sec" se O

ee | opal ones
al ay Y Yu

Fic. 8:.—Pedigree of a family with poorly nourished nails and hair (black
symbols),—NICOLLE ET HALIPRE.

Still another peculiarity of the skin is due to a positive
character. This is a thickening of the palms of the hands
and soles of the feet (Fig. 82). Here all, or half, of the
children of an affected parent are affected, but normals of
the strain, who marry outside of the family, will have no
thick-skinned children.

In some persons the color of the hair of the head is not
uniform, but there are patches of white hair in the midst

Inheritance of Physical and Mental Traits 275

of a prevailing brown head of hair. This spotted condition
is due to a positive factor, just like spottedness in mice.
From a spotted parent at least half the offspring are spotted;

Q Soe
PHOMOMMOONHMHO

Fic. 82.—Pedigree of a family with tyloses (T). Note that . Il affected per-
sons have at least one parent affected —UNnNa,

oe
gOo0m0m To
Sear oene eee ce
OO@meRHOO

O

~

Fic. 83.—Pedigree of faulty enamel of teeth. This peculiarity appears only
in the offspring of an affected parent, consequently it is a positive trait —TURNER.

but a person with uniform coat belonging to the spotted
strain will have no children with the white patch.

Probably the same law is followed in the case of families
without teeth and also in families with faulty enamel of the
teeth (Fig. 83). Apparently there is a determiner that

276 Heredity and Eugenics

partially or fully prevents the development of the tooth
germ.

Some peculiarities of the eye are clearly inherited.
Thus the condition in which the lens of the eye becomes
clouded and opaque seems to be due to a positive determiner,
and this is most clearly seen when cataract appears in
middle life. For, all cases of presenile cataract appear in the
offspring of affected persons, and two unaffected persons
probably never have descendants with cataract (Fig. 84).

Fic. Oy eae of a a with presenile cataract (black symbols).
Numbers in circles indicate unaffected individuals. Cataract in offspring of
affected parents only.

The same law holds for a peculiarity of the eye such that
the affected person cannot see by weak light, such as the
light of lamp, electric lights, etc. (night blindness). There
is clearly a positive determiner, since affected persons have
affected offspring, but if the parents are not affected (thus
proving the absence of the determiner from their germ
plasm), the offspring are never affected. These con-
clusions are based on the remarkable pedigree compiled
by Nettleship, involving over two thousand individuals.

Inheritance of Physical and Mental Traits 277

Many peculiarities of the skeleton are clearly due to a
positive determiner that inhibits the normal development.
Thus the case is cited of a father with a deformed clavicle
or collar bone; of his seven children, five have the clavicles
of a more or less abnormal form. Likewise in polydactyl-
ism, or extra-fingeredness, there is some positive factor
that induces the formation of the extra toe; but normal-
toed persons of a polydactyl strain, being without the
determiner, will have all children with five toes only.

The same is true of brachydactyly. There is something
that stops the growing of the fingers to the normal length,

i
cae i -
lad duceull -

Fic. 85.—Pedigree of a family with diabeles insipidus. D, affected persons

so that if the determiner gets into the zygote from either
side of the house, the child will be short-fingered, but not
otherwise.

Diabetes is a common disease which seems to belong
to this category (Fig. 85). Here again two normal parents
may have defective children but only when the defect occurs
in the germ plasm of both sides of the house.

The applications of these facts regarding abnormalities
and diseases that are of a positive sort have an importance
for eugenics. They are all characterized by this, that they
usually appear in each generation and do not skip genera-

278 Heredity and Eugenics

tions. They are relatively common in any given family,
since half or all of an affected fraternity commonly show
the trait. If the trait is an undesirable one and it must not
be reproduced, then the eugenical advice is for an affected
person to abstain from having children. But an unaffected
person belonging to this strain may marry an unaffected per-
son with impunity, and it is immaterial for the inheritance
of this trait whether they be cousins or not.

We have next to consider the class of abnormalities and
weaknesses that are due to the absence of a determiner, to
the disappearance of a trait that tends to normality. A
good example of such a defect is seen in albinism, already
referred to (Fig. 86). In this large pedigree the number of
affected individuals is small, and they are frequently derived
from two pigmented persons; cousin marriages are common.
The defect may be carried in the germ cells of two normal
parents; hence its appearance from such parents.

Another example is seen in Thomsen’s disease, a disease
that is characterized by a slow initial contraction of a
muscle after stimulus (Fig. 86). Here again two normal
consorts have some affected children and cousin marriages
are common.

There is reason for asserting that weakness of the mucous
membranes is due to a similar defect (Fig. 88). If both
parents are without the determiner for resistance, then of
course all offspring will be non-resistant. When one
parent is liable to colds and pneumonia and the other has
catarrh, the children suffer from tonsilitis, diphtheria, and
inflammations of the throat and lungs. But if one parent
be non-resistant, and the other, though resistant, have
some non-resistant germ cells, at least half of the offspring
will be non-resistant.

279

Inheritance of Physical and Mental Traits

copeuay & fayeur Pp

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280 Heredity and Eugenics

Some eye diseases are clearly due to a defect in the
determiner. Such is the case with an inflammatory con-
dition of the retina in which pigment is deposited and the
patient ultimately loses his sight
(Fig. 89). This disease fre-
quently appears in the children
of two normal persons who are
cousins, and consequently both

I Baie Tt carry the defect in their germ
- ® a =i ® cells.

Deaf-mutism also is due toa
_ Fic. 87.—Pedigree of Thom- defect; but the nature of the
sen’s disease (black symbols). Ap- : a , tase
pears in cousin marriages even defect is different in different
from affected parents; hencedueto cases. Deaf-mutism is so varied
a defect. Squares indica ales;
se catioy OE lane cae cae ctace Aiee Te frequently two unrelated
circles, females. —BERNHARDT. ‘
deaf mutes may have hearing
children (Fig. 90). But if the deaf-mute parents be
cousins, the chances that the
deafness is due to the same CO LhO

Colds \ Calerrh
unit defect are increased and

all of the children will probably eRe) ial C O CO Cl

taberc Colds \ Calarrh

be deaf. pal

We come now to consider a o C C OQ O 2

apth throat resp Ponsilihs fons htis

mental peculiarities, and here gty -e?ys oe,
at once enter a vast field in Fic. 88.—Pedigree showing
which surprising discoveries imheritance of a tendency toward
ae Wee ar : colds, catarrh, and respiratory
ave been made in recent years, diseases.

and which point to the cause of
many of our social difficulties and the way out.

First, consider the facts of feeble-mindedness. This
term is a lumber-room and comprises various mental defi-

ciencies, such as inability to count, to repeat phrases, to

Inheritance of Physical and Mental Traits 281

learn to write or to draw, to meet difficult situations by
intelligent adjustment, to control the appetites and passions,
to appreciate moral ir

ideas. Many persons 2 ©

who are not regarded oe

as feeble-minded have ! OP adie @ O O O
some of these or simi- peered

lar defects; the typi- 1@ ry CO OQ e e pe e

cally feeble-minded Fic. 89.—Pedigree of retinitis pigmentosa
are defective in several (black symbols) in a family described by
or many such mental Mooren.—NETTLESHIP.

traits. In what follows I shall use feeble-mindedness in
the latter sense.

From the studies of Dr. Goddard and others, it appears
that when both parents are feeble-minded all of the children
will be so likewise; this conclusion has been tested again and
again (Fig. 91). But if ove of the parents be normal and of

' O10 wt

on NN’ OO OD) Hye > >’

Wo geal-metism in

children or grond-
ca ldrer

Y N? N? N
Fic. 90.—Pedigree of a family with deaf mutes (D) in a large proportion of the
later generations.

normal ancestry, all of the children may be normal (Fig.
92); whereas, if the normal person have defective germ

282 Heredity and Eugenics

cells, half of his progeny by a feeble-minded woman will be

defective.
Epilepsy and feeble-mindedness may replace each other
(as equivalents) in pedigrees. This is well illustrated by

T T
d J
wh tnt

op

BOo; +o

Fic. 91.—Pedigree of a family with a high proportion of feeble-minded per-
sons (F). Squares, males; circles, females; d. inf., died in infancy —GopDarD.

here
joe a

T 1

N@eCOORE *.@ fa rh eee

da

Fic. 92.—Pedigree of a family in aa ac feeble-minded grandmother
married twice; by a normal husband she had normal children; but by an alco-
holic, sex-offending (Sx), doubtless feeble-minded husband she had only feeble-

minded children.—Gopparp.
the figure (Fig. 93) in which a feeble-minded sex offender
has by an epileptic daughter two feeble-minded children
and one epileptic child.

Many criminals, especially those who offend against the
person, are feeble-minded, as is shown by the way they

Inherttance of Physical and Mental Traits 283

occur in fraternities with feeble-mindedness, or have feeble-
minded parents (Fig. 94). The test of the mental condition

of relatives is one that may well be
applied by judges in deciding upon
the responsibility of an aggressor. It
is to be hoped that the conservatism
of the law upon this matter may be
speedily overcome.

Not only the condition of imper-
fect mental development, but also
that of inability to withstand stress
upon the nervous system, may be
inherited. From the studies of Dr.
Rosanoff and his collaborators, it ap-
pears that if both parents be subject
to manic depressive insanity or to
dementia precox, all children will be
neuropathic also (Fig. 95); that if

A ahO

Lrygole

TSEOOD
“b

unktown

anenceph.

Fic. 93.—The pedigree
of a family in whose second
generation incest produces
an epileptic daughter, but
by whose own father she
has one epileptic and two
feeble-minded children; A,
alcoholic; C, criminalistic;
E, epileptic; F, feeble-
minded; Sx, licentious.

one parent be affected and come from a weak strain, half

C0 DOO0

dm d0Ho 000000000

opudéagonc

Clon

SUPO ROG on

IO attempt 120 194
ted

crarefahutelute

towede

Fic. 94.—Pedigree of a feeble-minded family in which criminalistic (C) and

licentious (Sx) traits also appear.

284 Heredily and Eugenics

of the children are liable to go insane; and that nervous
breakdowns of these types never occur if both parents be
of sound stock.

Even the condition of general nervousness is an indica-
tion of a nervous weakness that is, apparently, due to the
absence of a determiner. Thus when a person belonging to
a neurotic strain marries a normal person whose father
died of apoplexy, some neurotic and feeble-minded children
may appear in the offspring.

Finally, a study of families with special abilities reveals
a method of inheritance quite like that of nervous defect.

a O) re)
CHOONXMONOONOORN

~

Fic. 95.—Pedigree of a family in which the father’s parents (upper left) are
both nervous (N) and have four nervous children. The mother is nervous; so were
her father and four of her brothers and sisters, while one is insane. Of the three
grandchildren one is insane (I), one epileptic (E), and one extremely nervous (N).—
CANNON AND ROSANOFF.

If both parents be color artists, or have a high grade of
vocal ability or are littérateurs of high grade, then all of
their children tend to be of high grade also. If one parent
has high ability, while the other has low ability but has
ancestry with high ability, part of the children will have
high ability and part low. It seems like an extraordinary
conclusion that high ability is inherited as though due to
the absence of a determiner in the same way as feeble-
mindedness and insanity are inherited. We are reminded
of the poet: “Great wits to madness sure are near allied.”
Evidence for the relationship is given by pedigrees of men

Inheritance of Physical and Mental Traits 285

of genius that often show the combination of ability and
insanity (Fig. 96). May it not be that just that lack of
control that permits “flights of the imagination”’ is related
to the flightiness characteristic of those with mental weak-
ness or defect ?

These studies of inheritance of mental defect inevitably
raise the question how to eliminate the mentally defective.
This is a matter of great importance because, on the one
hand, it is now coming to be recognized that mental defect

Swicide

Soler

PJurde

Proei igner

OB 00RBO OBO

O,0, 0,0 0,0
sma bo | eee Oto

mechan, saventive Bare over 2byrs, bu
ability ability bun Sie hore mechan abihty, ability
b00r builders, €r.

Ot SF yrs.
dasigning boats,

Fic. 96.—Pedigree of a family with great inventive and artistic ability, in
whose earlier generations appear insanity (I), suicidal tendency, and eccentricity.

is at the bottom of most of our social problems. Extreme
alcoholism is usually a consequence of a mental make-up
in which self-control of the appetite for liquor is lacking.
Pauperism is a consequence of mental defects that make
the pauper incapable of holding his own in the world’s
competition. Sex immorality in either sex is commonly
due to a certain inability to appreciate consequences, to
visualize the inevitableness of cause and effect, combined
sometimes with a sex-hyperaesthesia and lack of self-control.

280 Heredily and Eugenics

Criminality in its worst forms is similarly due to a lack of
appreciation of or receptivity to moral ideas.

If we seek to know what is the origin of these defects,
we must admit that it is very ancient. They are probably
derived from our apelike ancestors in which they were
normal traits. There occurs in man a strain that has not
yet acquired those traits of inhibition that characterized
the more highly developed civilized persons. The evidence
for this is that, as far back as we go, we still trace back the
black thread of defective heredity.

We have now to answer the question as to the eugenical
application of the laws of inheritance of defects. First,
it may be pointed out that traits due to the absence of a
determiner are characterized by their usual sparseness in
the pedigree, especially when the parents are normal; by
the fact that they frequently appear where cousin marriages
abound, because cousins tend to carry the same defects
in their germ plasm though normal themselves; by the
fact that two affected parents have exclusively normal
children, while two normal parents who belong to the same
strain, or who both belong to strains containing the same
defect, have some (about 25 per cent) defective children.
But a defective married to a pure normal will have no
defective offspring.

The clear eugenical rule is then this: Let abnormals
marry normals without trace of the defect, and let their
normal offspring marry in turn into strong strains; thus
the defect may never appear again. Normals from the
defective strain may marry normals of normal ancestry;
but must particularly avoid consanguineous marriages.

The sociological conclusion is: Prevent the feeble-
minded, drunkards, paupers, sex-offenders, and criminalistic
from marrying their like or cousins or any person belonging

Inheritance of Physical and Mental Traits 287

to a neuropathic strain. Practically it might be well to
segregate such persons during the reproductive period for
one generation. Then the crop of defectives will be reduced
to practically nothing.

I cannot close without referring to a remarkable method
of inheritance of human traits, namely, the sex limited.
As everyone knows, there are certain traits, such as facial
hair, which are associated with one sex; and a tendency
to heavy growth of beard may be transmitted by a mother’s
germ cells to her son. In this case the determiner for heavy

beard does not develop
in the female, but only 2s
in the male, under the |
. . U
stimulus, as it were, ® @) N

of the testicular se-
cretions; or perhaps El ® 5 B) @ fal ® doe El B)
in the absence of an
inhibiting enzyme

secreted by the ovary.
But in another class of cases the inheritance is most

complex. Thus usually only males are color-blind, but
they do not transmit their condition to their sons. On
the other hand, the normal women of this strain will have
color-blind sons (Fig. 97).

This has been a great mystery, but thanks to the recent
studies in sex chromosomes by Wilson, Morgan, and others,
it is a mystery no longer. It is explained by one fact and
one hypothesis. The fact is that the male has only one
sex chromosome, while the female has two. The hypothesis
is that a factor for distinguishing colors is lacking in the
affected male and is lost out of the single sex chromosome
of such a male. Now the consequence of these two prin-
ciples can be seen easily. Let the striated disk (S, Fig. 98)

FIG. 97. ea ie family ae re
blindness (B).

288 Heredity and Eugenics

stand for the single male sex chromosome, which, by hypothe-
sis, lacks the color distinguishing factor. Let the white
disk (IV) symbolize the absence of a chromosome in a germ
cell. Let the black disks (B) represent the two female
sex chromosomes with the factor of color-sight. Then the
union of S+8B gives the female sex and has the determiner
for color, albeit simplex. The union W+B gives the male
sex and also has the determiner for color-sight. Hence
neither sons nor daughters of a color-

3 ; ;
? blind man are color-blind. If the son
5 @ @» marry a normal woman, it is clear
uO @: that (since no S comes into the union)

the children are normal. But if the
ee ae ae daughters marry, half of the males
ing sex-limited characters. Will receive the single S chromosome
The circles represent sex and such will be color-blind. Thus
chromosomes. F
the long famous knight’s move form
of heredity of color-blindness is explained. Several other
traits are inherited in the same way: bleeding, imperfect
development of the iris, and atrophy of the optic nerve.
In all these cases unaffected males may marry with impun-
ity; but females of the strain who have affected brothers
should not have children.

The foregoing considerations bring clearly to mind the
great advance that has been made in recent years in the
analysis of the inheritance of traits. At last it is possible
to give definite advice to those about to marry, or who do
not wish to transmit their undesirable traits. Of the
method of inheritance of many traits we are still in ignor-
ance. In the absence of detailed knowledge, the best gen-
eral advice that can be given is this; marry dissimilars.
Weakness in any trait should marry strength in that trait;
and strength may marry weakness.

CHAPTER IX
THE GEOGRAPHY OF MAN IN RELATION TO EUGENICS:

RELATIONS OF BARRIERS TO HUMAN BREEDING

In the period before our Civil War, while men were
looking for an excuse if not a justification for slavery the
subject of the unity of man’s species was much discussed.
In these later days, removed from the passions of politics,
as a purely academic question the inquiry has been reopened.
Ideas have changed much in the intervening fifty or sixty
years and now we have to define all over again what is
meant by species or race.

In connection with the new ideas of heredity we have
gained a new conception of species and race. We now
apply the terms indifferently and say a species, or race, is
an intergenerating group of individuals distinguished by
the possession of one or more unit-characters. As we look
over mankind we note at once the groups that have always
been distinguished: the Negroes with black skin and woolly
hair; the oriental race with olive or yellow skin and (typi-
cally) narrow eyes; the American Indian with brown-red
skin and long straight hair, and the Caucasians with white
skin and high cephalic index. This naive classification
may have sufficed for the dawn of anthropology, but today
we recognize its insufficiency. In the group of Caucasians
are hundreds of distinctive characters upon each of which
a race might be founded. There are the brunette skin and

*Much of the present chapter is reprinted from the author’s book, Heredily
in Relation to Eugenics, and it appears here through the courtesy of the publishers

of that book, Messrs. Henry Holt & Co.
289

290 Heredity and Eugenics

the blonde; the straight hair and the curly; the flaxen
hair and the brown and the red; the blue eyes and the dark;
the straight nose, the aquiline, and the pug; the broad
head and the high and the narrow; the thin lips and the
thick, and so through the categories. ‘The only reason why
we do not have distinct species of men distinguished by
such traits is because of the extensive hybridization that
man is undergoing. Everywhere, brown eyes mate with
blue, black hair with flaxen, curly with straight, and so on.
Man’s potential races are not realized just because of the
universal interfertility of the different races and because
of the mobility of man’s habitat.

Now is there any evidence aside from a-priori consid-
erations for testing this view? Are the potentialities that
we assume anywhere realized? Is the theory of man’s
universal hybridization more than a figment of the imagi-
nation ?

First, let us admit that evidence for the unity of, say,
the Caucasian race has been offered by the biometricians.
They have said if the race is homogeneous it will show itself
by the biometric test. Measure a trait in 10,000 individ-
uals; and plot the relative frequency of the different values
found. If that frequency rises in a gentle curve from its
lowest value to a maximum at some middle value and then
falls again smoothly to the highest value the curve is a
simple curve and this has been regarded as proving a unit-
population. But it does not prove it; for we now realize
that even the apparently simple curve may be the result-
ant of many more elementary curves whose number dimin-
ishes uniformly on both sides of the center. The elementary
curves are the ones that include the fluctuations of the real
units.

Geography of Man in Relation to Eugenics 291

Second, the real units may be isolated by the simple
process of preventing the random hybridization and ensuing
breeding within the type. This result has been nearly
realized in small oceanic islands, and in other isolated
communities. It will be interesting to look at some of
these isolated places and learn what has been produced in
them.

At Swans’ Island, Maine, much consanguinity in mar-
riage occurs; cousin marriages are the rule. A consequence
has been that the defect of feeble-mindedness is unusually
common and, were the process to continue for many more
generations, a race with this trait, among others, would
doubtless become established.

At Western Martha’s Vineyard a careful genealogical
study has been made by Dr. Alexander Graham Bell and
much consanguineous marriage has been found. Here is,
or was, being formed a deaf-mute colony; one out of every
twenty-five was already a deaf mute.

At Block Island, with a population of fifteen hundred,
much consanguineous marriage has occurred, and a non-
fecund strain has been isolated. On the Banks off Palmico
Sound consanguineous marriage occurs with extraordinary
frequency; and a strain characterized by suspicion, insan-
ity, and mental dulness is being formed. At George Island
near Eleuthera Island, one of the Bahamas, long inbreed-
ing has produced a race that tends toward dwarf stature
and eye defects, including cataracts.

What is true of islands holds for other isolated situations.
A physician at an extreme point of the peninsula of Dor-
chester County, Maryland, writes that marriages there are
usually consanguineous and a race of dwarfs and cripples
is being formed. Mountain valleys of the Ramapo, Cats-

292 Heredity and Eugenics

kill, Taconic, and Adirondack masses show many endoga-
mous centers. In one place a race of criminals is being
formed; in another a feeble-minded strain; in another an
albino race, and so on. There is reason for thinking that
the valleys of eastern Kentucky and Tennessee are centers
of inbreeding and nearly pure races are being formed there.
In larger settled countries the process has gone farther.
From the Chin Hills, Burmah, one hears: “Rau Vau Village
has been isolated for about seven generations. It contains
about sixty houses and possibly two hundred inhabitants.
Of these ten are idiots, many are dwarfs, and some hydro-
cephalic. A number of cases of syndactylism or webbing
of hands, and brachydactyly occur.”

Only slightly less important than the geographical barriers
are the social. A public institution brings together men and
women so intimately that marriages frequently occur after
leaving the institution. Thus two persons with the same
trait become parents. Almshouses in which segregation of
the sexes is imperfect yield numerous depauperate and
imbecile offspring, and there is reason for suspecting that
sanatoria and some hospitals for the “curable” insane
lead to marriage of two weak persons. That institutions
for the deaf lead to the marriage of similarly defective
is notorious. Thus Dr. Bell, who has long warned us of
the imminent danger of the formation of a deaf variety
of the human race in America, says: “I desire to direct
attention to the fact that, in this country deaf mutes marry
deaf mutes. An examination of the records of some of our
institutions for the deaf and dumb reveals the fact that
such marriages are not the exception but the rule.”

The barrier of language is extremely important in pro-
moting consanguineous marriages, or the matings of persons

}
Geography of Man in Relation to Eugenics 203

with the same defect. Thus with regard to deaf mutes,
Bell says: ‘‘The practice of the sign language hinders the
acquisition of the English language; it makes deaf mutes
associate together in adult life, and avoid the society of
hearing people; it thus causes the intermarriage of deaf
mutes and the propagation of their physical defect.”” The
importance of this barrier is seen among recent immigrants.
These tend to herd together, largely because of a desire to be
with people who speak the same language. Thus immigration,
instead of directly tending to promote matings of dissimilar
and unrelated blood, has, at first, an exactly opposite effect.

The barrier of race is of the very greatest importance in
promoting marriages of kin—especially if one race be in a
marked minority, as the Negroes are in New Hampshire
and the whites are in the Mississippi River bottom, around
Vicksburg, or in parts of the West Indies.

Finally the barrier of religious sect has been erected
again and again to insure the intermarriage of the faithful
only. This is illustrated by the teachings of the Society
of Friends and smaller sects, such as the Dunkers, Shakers,
and Amish. Of the Dunkers it is written: ‘In their early
history marriage out of the church was punishable by
expulsion.’ It is still frowned upon but the process of
liberalization now in progress had modified the attitude of
the church. In some congregations families intermarry
generation after generation. But the degree of kinship is
not so close that any evil results appear in the offspring.”’
Nevertheless one sees the danger that any small sect
with such tenets runs. A critical study of the Amish of
Pennsylvania with much marriage of kin shows a sufficient
progeny of epilepsy and crippled children to serve as a

tChronicon Ephratense, 96, 246.

204 Heredity and Eugenics

warning that a defect is in the blood of some of the strains
that in time will affect the entire sect who remain in that
part of the country.

MIGRATIONS AND THEIR EUGENIC SIGNIFICANCE

The human species has come to occupy the entire
habitable globe. This fact is mute testimony of man’s
migratory capacity and tendencies. Just as the Norwegian
lemming has been observed, in consequence of several
years of favorable conditions for breeding in its mountain
home, to spread over the surrounding territory in great
bands, seeking less crowded breeding grounds; even as the
army worm and the grasshopper swarm from their native
territory; so man, also, under the pressure of crowded
conditions, poverty, and oppression, or lured by brighter
prospects elsewhere, may move in hordes to other lands
that seem to offer better opportunities. Thus Asia seems
to have debouched her surplus population upon Europe
in the shape of the Huns during the fourth and fifth cen-
turies of our era and the Turks during the fourteenth and
fifteenth centuries. So the Anglo-Saxons and the Normans
successively swarmed upon England. So, among savages,
the Masai of Africa moved upon the neighboring tribes and
established themselves over much of southeastern Africa.
So in the last three centuries the Americas and Australia
have witnessed the greatest migrations that the world has
ever seen, hundreds of thousands annually coming from
overcrowded Europe, and Asia to the ‘“‘ New World.”

For us in America the phenomena of migration should
have a special interest. Excepting for the few scores of
thousands of Indians there was a continent devoid of a
population—a clean slate upon which history was to be

Geography of Man in Relation to Eugenics 205

written and where the effect of “blood” in determining
that history might be traced.

Since the first few scores of thousands of immigrants
had the greatest influence on the ideals of the colonies they
established and since their blood has had the longer time
to show its effect, and since their traits have had the great-
est chance to disseminate widely, they deserve special
consideration.

On the James River the first settlers consisted chiefly
of ‘“‘discredited idlers and would-be adventurers,’ more
than half of them “gentlemen” of good family but untrained
in labor, trusting for a change of fortune in the new land.
Even later, men, women, and children were sent by the
London Company to colonize the new land and that com-
pany was not particular as to quality. Even felons, mur-
derers, and women of the streets were at times sent over
from London to relieve the city of them, and the governor,
who was a pure euthenist and seemed to think the better
environment would cure their evil ways, welcomed all.

But a better blood soon crowded into Virginia to redeem
the colony. Upon the execution of Charles I (1649) a host
of royalist refugees sought an asylum here, and the immi-
gration of this class continued even after the Restoration.
By this means the province was enriched by a germ plasm
which easily developed such traits as good manners, high
culture, and the ability to lead in all social affairs—traits
combined in remarkable degree in the “first families of
Virginia.” From this complex and the similar complex
of Maryland has come much of the bad blood that found
the retreats of the mountain valleys toward Kentucky and
Tennessee to its liking and that spread later into Indiana
and Illinois and gave rise, in all probability, to the Ishmael-

296 Heredity and Eugenics

ites, a family of which hundreds have been supported in
the almshouses and jails of Indiana. From this complex
came also some of America’s greatest statesmen and war-
riors, the Randolphs, the Marshalls, the Madisons, the
Curtises, the Lees, the Fitzhughs, the Washingtons, and
many others born with the instinct to command. Such
are the descendants of the high-spirited cavaliers. It might
have been predicted that the future state would be “the
Mother of Presidents,” and that in a civil war the severest
battles should be fought on her soil.

Farther north, at Manhattan Island, a settlement was
being made by another sort of people: a band of Dutch
traders. The fur trade with the Indians waxed profitable.
The more venturesome established trading-posts up the
North River, even as far as the present site of Albany;
others went east as far as the Connecticut River. They
maintained friendly relations with the Indians, as the main
source of their wealth, and under their protection estab-
lished trading-posts, even along the valley of the Mohawk.
Little wonder that such blood, under the favorable environ-
ment of an admirable location, has created the commercial
center of the western world.

On the bleak coasts of New England were being founded
settlements of idealists, men who were willing to undergo
exile for conscience’ sake. They included many scholars
like the pastor Robinson; Brewster who, while self-exiled
at Leyden, instructed students at the University; John
Winthrop, “of gentle breeding and education”; John
Davenport, of New Haven, whom the Indians named
“heap study-man.” Little wonder that the germ plasm
of these colonies of men of deep convictions and scholar-
ship should show its traits in the great network of its

Geography of Man in Relation to Eugenics 207

descendants and establish New England’s reputation for
conscientiousness and love of learning and culture. As it
was almost the first business of the founders of the colonies
of Massachusetts Bay and New Haven to found a college,
so their descendants—the families of Edwards, Whitney,
Dwight, Eliot, Lowell, Woolsey, and the rest—have not
only led in literature, philosophy, and science, but have
carried the lamps of learning across the continent, light-
ing educational beacons from Boston to San Francisco.
Nor is it an accident that on the soil tilled by these dis-
senters from the Established Church of England should be
spilled the first blood of the American Revolution.

Later, to the shores of the Delaware, Penn led his band
of followers, consisting of men and women whose natures
were attracted to his principles of thrift, absence of show,
and non-resistance. The germ plasm of his followers soon
peopled Penn’s woods, and it is not due solely to chance
that Pennsylvania has the largest number of homes owned
by their occupants and free from debt of any state.

Thus the characteristics of each commonwealth were
early determined by the traits of the persons who were
attracted toward them. These traits still persist in their
dwindling descendants who strive to secure the preservation
in the state of the ideals inculcated by their forefathers.

One common characteristic these early immigrants had,
which led them to leave family and friends, to undergo the
trials of the long sea voyage in small ships and to settle in
a rigorous climate among unreliable savages, and that was a
willingness to break with tradition, to exchange the old for
the new and better. This trait, that amounts in extreme
cases to a wanderlust, is illustrated by the history of many
a pioneer. For example, Simeon Hoyt landed in Salem,

298 Heredity and Eugenics

Mass., in 1628; went in the first company of settlers to
Charleston (1629); went to Dorchester (1630) with the first
company of settlers there; joined the church at Scituate
(1635), and built a house there; then, probably in the
spring of 1636, migrated to Windsor, Connecticut Colony,
which he helped found. In 1649 he was granted land at
Fairfield, and in 1657 he died at Stamford. Thus in the
space of thirty years Simeon Hoyt lived in seven villages
in America and was a founder of at least three of them—
a truly restless spirit, like many another settler, and the
parent of a restless progeny!

Still another example is that of Hans Jorst Heydt of
Strasburg. He fled to Holland when his native town was
seized by Louis XIV, married there Anna Maria DuBois,
a French Huguenot refugee from Wicres, and came with
her to America and settled at New Paltz on the Hudson
about 1710. Schismatic dissensions having broken out in
the new colony, Heydt, with others, left and settled, about
1717, in Philadelphia County, not far from Germantown,
where he acquired several hundred acres of land, estab-
lished a colony, built mills, and entered upon various com-
mercial enterprises of magnitude. In 1731, having acquired
a grant of forty thousand acres of land in the Shenandoah
Valley, he migrated thither, became known as Baron Hite,
and died there in 1760. One of his friends, Van Metre,
who originally settled at New Paltz, had moved first to
Somerset County, New Jersey, then to Salem County in
the same colony; later to Prince George’s County, Mary-
land, and, finally, to Orange County, Virginia. These are
examples, merely, of the restlessness—often enterprising
restlessness—of the early settlers, and it persists in their

descendants.

Geography of Man in Relation to Eugenics 299

Now all of these migrations have a profound eugenic
significance. The most active, ambitious, and courageous
blood migrates. It migrated to America and has made her
what she has become; in America another selection took
place in the western migrations, and what this best blood
—this créme de la créme—did in the West all the world
knows. Great cities like Chicago, with its motto “T will,”
arose in a generation or two to the front rank of world
metropolises, and New England, the early home of the
sewing machine and the cotton gin, has yielded the palm
to the Central West, the home of the reaping machine and
the aeroplane.

And when the best and strongest migrated the weaker
minds were left behind to breed in the old homestead. A
recent report of the British “Committee on Physical
Deterioration” contains the testimony of Dr. C. R. Browne
about conditions in the west of Ireland. He says: ‘The
sound and the healthy—the young men and young women
from the rural districts emigrate to America in tremendous
numbers, and it is only the more enterprising and the more
active that go, as a rule.” And Dr. Kelly, the Roman
Catholic bishop of Ross testified: “ For a considerable number
of years it has been only the strong and vigorous that go—
the old people and the weaklings remain behind in Ireland.”
And even in New England we see signs of decadence of the
old stock and men speak of racial deterioration. But the
race as a whole has not deteriorated but only the New
England representatives—the left-behinds of the grand old
families, whose stronger members went west.

Likewise in the rural and semi-rural population within
a hundred miles of our great cities, we find a disproportion
of the indolent, the alcoholic, the feeble-minded, the ne’er-

300 Heredity and Eugenics

do-well. Thus our great cities lure to themselves the best
of the rural protoplasm and surround it with conditions that
discourage reproduction, either by creating a disinclination
to marriage or making it inconvenient and expensive to have
children. So our great cities act anti-eugenically, sterilizing
the best and leaving the worst to reproduce their like.

THE INFLUENCE OF THE SINGLE GERM PLASM ON THE RACE

As one stands at Ellis Island and sees pass the stream
of persons, sometimes five thousand in a day, who go
through that portal to enter the United States and, for the
most part, to become incorporated into it, one is apt to
lose sight of the potential importance to this nation of the
individual, or, more strictly, the germ plasm that he or
she carries. Yet the study of extensive pedigrees warns
us of the fact. Every one of those peasants will, if fecund,
play a réle for better or worse in the future history of this
nation. Formerly, when we believed that traits blend,
a characteristic in the germ plasm of a single individual
among thousands seemed not worth considering—it would
soon be lost in the melting-pot. But now we know that
unit-characters do not blend; that after a score of gener-
ations the given characteristic may still appear unaffected
by the repeated union with foreign germ plasm. So the
individual, as the bearer of a potentially immortal germ
plasm with immutable traits, becomes of the greatest
interest. A few examples will illustrate this law and its
practical importance.

Elizabeth Tutile——From two English parents, sire at
least remotely descended from royalty, was born Elizabeth
Tuttle. She developed into a woman of great beauty, of
tall and commanding appearance, striking carriage, ‘of

Geography of Man in Relation to Eugenics 301

strong will, extreme intellectual vigor. On November
19, 1667, she married Richard Edwards of Hartford, Con-
necticut, a lawyer of high repute and great erudition. Like
his wife he was very tall, and as they both walked the
Hartford streets their appearance invited the eyes and
admiration of all.” In 1691, Mr. Edwards was divorced
from his wife. After his divorce Mr. Edwards remarried
and had five sons and a daughter by Mary Talcott, a medi-
ocre woman, average in talent and character and ordinary
in appearance. None of Mary Talcott’s progeny rose
above mediocrity and the descendants gained no abiding
reputation.

Of Elizabeth Tuttle and Richard Edwards the only son
was Timothy Edwards, who graduated from Harvard College
in 1691, gaining simultaneously and highly exceptionally
the two degrees of Bachelor of Arts and Master of Arts.
He was pastor of the church in East Windsor, Connecticut,
for fifty-nine years. Of his eleven children the only son
was Jonathan Edwards, one of the world’s great intellects,
pre-eminent as a divine and theologian, president of Prince-
ton College. Of the descendants of Jonathan Edwards
much has been written; a brief catalogue must suffice:
Jonathan Edwards, Jr., president of Union College;
Timothy Dwight, president of Yale; Sereno Edwards
Dwight, president of Hamilton College; Theodore Dwight
Woolsey, for twenty-five years president of Yale College;
Jared Sparks, president of Harvard College, 1849-53;
Sarah, wife of Tapping Reeve, founder of Litchfield Law
School, herself no mean lawyer; Daniel Tyler, a general of
the Civil War and founder of the iron industries of northern
Alabama; Ann Maria, wife of Edwards Amasa Park,
president of Andover Theological Seminary, herself as

302 Heredity and Eugenics

astute a thinker as her clerical spouse; Timothy Dwight the
second, president of Yale University from 1886 to 1898;
Theodore William Dwight, founder and for thirty-three
years warden of Columbia Law School; Henrietta Frances,
wife of Eli Whitney, inventor of the cotton gin, who, burn-
ing the midnight oil by the side of her ingenious husband,
helped him to his enduring fame; Merrill Edward Gates,
president of Amherst College; Catherine Maria Sedgwick,
of graceful pen; Charles Sedgwick Minot, authority on
biology and embryology in the Harvard Medical School;
Edith Kermit Carow, wife of Theodore Roosevelt, and
Winston Churchill, the author of Coniston. These consti-
tute a glorious galaxy of America’s great educators, students,
and moral leaders of the Republic.

The remarkable qualities of Elizabeth Tuttle were in
the germ plasm of her four daughters also: Abigail Stough-
ton, Elizabeth Deming, Ann Richardson, and Mabel Bige-
low. All of these have had distinguished descendants of
which only a few can be mentioned here. Robert Treat
Paine, signer of the Declaration of Independence, was
descended from Abigail; the Fairbanks Brothers, manu-
facturers of scales and hardware at St. Johnsbury, Ver-
mont, and the Marchioness of Donegal were descended
from Elizabeth Deming; from Mabel Bigelow came Morri-
son Waite, chief justice of the United States, and the law
author, Melville M. Bigelow; from Ann Richardson pro-
ceeded Marvin Richardson Vincent, professor of Sacred
Literature at Columbia University and the Marchioness of
Apesteguia, of Cuba. Thus, numerous scholars, inventors,
and publicists trace back their origin to the germ plasm from
which (in part) Elizabeth Tuttle also was derived, but of
which, it must never be forgotten, she was not the author.

Geography of Man in Relation to Eugenics 303

The first families of Virginia.—This remarkable galaxy
arose by the intermarriage of representatives of various
English aristocratic families. The story of these early
matings is briefly as follows: Richard Lee, of a Shropshire
family that held much land, and many of whose members
had been knighted, went, during the reign of Charles I, to
the colony of Virginia as secretary and one of the king’s
Privy Council. ‘‘He was a man of good stature, comely
visage, enterprising genius, sound head, vigorous spirit,
and generous nature.” He gained large grants of land
in Virginia. His son, Richard, married in 1674, Laetitia,
daughter of Henry Corbin and Alice Eltonhead. The
Corbins were wealthy and extensive landowners in England
for fourteen generations, and the Eltonheads were also an
aristocratic family and extensive landowners of Virginia,
holding high offices in the colony.

Richard and Laetitia Lee had six sons and one daughter,
Ann. Ann married Col. William Fitzhugh, a descendant
of the English barons, military men, and parliamentarians
of that name. Their eldest son married a Carter, and one
of their granddaughters and one of their sons married a
Randolph; their daughter, Mary, married George Washing-
ton Parke Custis, and became the grandmother of Robert
E. Lee. Richard Lee, Jr., had children who married into the
families of Fairfax and Turberville. A brother of Richard,
Thomas, was president of the council and at one time acting
governor of the colony. He married Hannah Ludwell,
descendant of a brother of the statesman, Lord Cottington;
one of their sons, Richard Henry Lee, prepared at the
Continental Congress the resolutions for independence;
another, Francis Lightfoot Lee, was a member of Congress;
and still another, Thomas, a judge of the General Court.

304 Heredity and Eugenics

Another son of Richard and Laetitia Lee was Henry,
who married Mary Bland, a descendant of Sir Thomas
Bland, and a granddaughter of Theodorick Bland, speaker
of the House of Burgesses and member of the Council.
Their three sons were all members of the House of Bur-
gesses and some were in the House of Delegates, in con-
ventions and in the state senate. Such was the product
of the first families of Virginia—statesmen, military men—
the necessary product of their germ plasm.

The Kentucky aristocracy.—Nearly two centuries ago,
John Preston of Londonderry, Irish born though English
bred, married the Irish girl, Elizabeth Patton, of Donegal,
and to the wilderness of Virginia took his wife and built
their home, Spring Hill.

Of this union there were five children: Letitia, who married
Colonel Robert Breckinridge; Margaret, who married Rev. John
Brown; William, whose wife was Susannah Smith; Anne, who mar-
ried Colonel John Smith; and Mary, who married Benjamin Howard.
. . .. From them have come the most conspicuous of those who bear
the name of Preston, Brown, Smith, Carrington, Venable, Payne,
Wickliffe, Wooley, Breckinridge, Benton, Porter, and many other
names written high in history.

They were generally persons of great talent and thoroughly edu-
cated; of large brain and magnificent physique. The men were
brave and gallant, the women accomplished and fascinating and
incomparably beautiful. There was no aristocracy in America that
did not eagerly open its veins for the infusion of this Irish blood; and
the families of Washington and Randolph, and Patrick Henry, and
Henry Clay, and the Hamptons, Wickliffes, Marshalls, Peytons,
Cabells, Crittendens, and Ingersolls felt proud of their alliances with
this noble Irish family.

They were governors and senators and members of Congress, and
presidents of colleges and eminent divines, and brave generals from
Virginia, Kentucky, Louisiana, Missouri, California, Ohio, New York,
Indiana, and South Carolina. There were four governors of old

Geography of Man in Relation to Eugenics 305

Virginia. They were members of the cabinets of Jefferson, and
Taylor, and Buchanan, and Lincoln. They had major-generals and
brigadier-generals by the dozen; members of the Senate and House
of Representatives by the score; and gallant officers in the army and
navy by the hundred. They furnished three of the recent Demo-
cratic candidates for Vice-President of the United States.

The quotation has a scientific value in comparison with
the product of Elizabeth Tuttle. The New England family
glows with scholars and inventors; the Virginia and Ken-
tucky families with statesmen and military men. The
result is not due merely to the difference in the character-
istics of Elizabeth Tuttle, Richard and Laetitia Lee, John
and Elizabeth Preston respectively, but to the different
traits of the New England settlers as a whole, and the Vir-
ginia cavalier-colonists as a body. The initial person
becomes a great progenitor largely because of some fortu-
nate circumstance of personal gift or excellent reputation
that enables his offspring to marry into the “best blood.”

The Jukes.—On the other hand, we have the striking
cases of families of defectives and criminals that can be
traced back to a single ancestor. The case of the ‘‘ Jukes”’
is well known. We are first introduced to a man known
in literature as ‘‘ Max,” living as a backwoodsman in New
York state, and a descendant of the early Dutch settlers;
a good-natured, lazy sot, without doubt of defective mental-
ity. He has two sons who marry two of six sisters whose
ancestry is uncertain, but of such a nature as to lead to
the suspicion that they are not full sisters. One of these
sisters is known as “Ada Juke,” also as “Margaret, the
mother of criminals.”” She was indolent and a harlot before
marriage. Besides an illegitimate son she had four legiti-
mate children. The first, a son, was indolent, licentious,
and syphilitic; he married a cousin and had eight children,

306 Heredity and Eugenics

all syphilitic from birth. Of the seven daughters, five were
harlots and of the others one was an idiot and one of good
reputation. Their descendants show a preponderance of
harlotry in the females and much consanguineous marriage.
The second son was a farm laborer, was industrious, and
saved enough to buy fourteen acres of land. He married
a cousin and they produced three still-born children, a
harlot, an insane daughter who committed suicide; an
industrious son, who, however, was licentious, and a pauper
son. The first daughter of “Ada” was an indolent harlot
who later married a lazy mulatto and produced nine children,
harlots and paupers, who produced in turn a licentious
progeny.

Ada had an illegitimate son who was an industrious and
honest laborer and married a cousin. Two of the three
sons were licentious and criminalistic in tendency, and the
third while capable, drank and received outdoor relief.
All of the three daughters were harlots or prostitutes, and
two married criminals. The third generation shows the
eruption of criminality. Excepting the children of the
third son, none of whom was criminalistic, we find among
the males twelve criminals, one licentious, five paupers,
one alcoholic, and one unknown; none was a normal citizen.
Among the females, eight were harlots, one a pauper, one
a vagrant, and two unknown; none was known to be
reputable. Thus it appears that criminality hes in the
illegitimate line from Ada, and not at all in the legitimate
—doubtless because of a difference in germ plasm of the
fathers.

The progeny of the harlot, Bell Juke, is a dreary monot-
ony of harlotry and licentiousness to the fifth generation.
Two in the fourth generation there are, and two in the fifth,

Geography of Man in Relation to Eugenics 307

against whom there is nothing and their progeny mostly
moved to another neighborhood and are lost sight of.
Very likely they have married into stronger strains and are
founders of reputable families.

The progeny of Effie Juke and the son of Max (a thief)
show to the fifth generation a different aspect. Some larceny
and assault there are, and not a little sexual immorality, but
pauperism is the prevailing trait.

Thus, in the same environment, the descendants of the
illegitimate son of Ada are prevailingly criminal; the pro-
geny of Bell are sexually immoral; and the offspring of
Effie are paupers. The difference in the germ plasms deter-
mine the difference in the prevailing trait. But however
varied the forms of non-social behavior of the progeny of
the mother of the Juke girls, the result was calculated to
cost the state of New York over a million and a quarter of
dollars in seventy-five years—up to 1877, and their proto-
plasm has been multiplied and dispersed during the subse-
quent thirty-four years, and is still going on.

The Ishmaelites—As another example of a great family
tracing back to a single man may be taken ‘The Tribe
of Ishmael” of central Indiana, as worked out, under
the direction of Rev. Oscar C. McCulloch, of the Charity
Organization Society, Indianapolis. The progenitor of this
tribe, Ben Ishmael, was in Kentucky as far back as 1790,
having come from Maryland through Kentucky. One of
the sons, John, married a half-breed woman, and came into
Marion County, Indiana, about 1840. His three sons who
figure in this history married three sisters from a pauper
family named Smith. They had altogether fourteen chil-
dren who survived, sixty grandchildren, and thirty great-
grandchildren, living in 1888.

308 Heredity and Eugenics

Since 1840, this family has had a pauper record. They have been
in the Almshouse, the House of Refuge, the Woman’s Reformatory,
the penitentiaries, and have received continuous aid from the town-
ships. They are intermarried with the other members of this group,

. and with over two hundred other families. In this family
history are murders, a large number of illegitimacies, and of prostitutes.
They are generally diseased. The children die young. They live
by petty stealing, begging, and ash-gathering. In summer they
“gypsy”? or travel in wagons, east or west. We hear of them in
Illinois about Decatur and in Ohio about Columbus. In the fall
they return. They have been known to live in hollow trees, on the
river bottoms or in empty houses. Strangely enough, they are not
intemperate to excess.

Ah, that in the hordes pressing at the gate at Ellis
Island, we could distinguish the John Prestons from the
Ben Ishmaels of the future!

THE EUGENICS MOVEMENT

Since the time of Plato there have not been lacking
persons who have urged that the human race would be
improved were more attention paid to marriage matings.
But, in recent years, these ideas have become so widespread
and have been urged with such vigor, as to warrant us in
speaking of a present eugenics movement. There are two
chief impulses, it seems to me, for this modern movement,
both world-wide. The first of these is a conviction that
there is a great proportional increase in feeble-mindedness
in its numerous forms—a great spread of animalistic traits—
and of insanity. en a state like New York spends one-
S of its state income for the care of the insane it is
not strange that many of its citizens are inquiring why this
is and whether there is any end to the increasing proportion
of the state’s income that must be spent in caring for those
who cannot aid themselves. The proportion of those who

are feeble-minded in such various directions as to constitute

Geography of Man in Relation to Eugenics 309

the feeble-minded class is estimated at 3 per cent of our
population, and were we to include drunkards, paupers,
grave sex-offenders, the criminalistic, the insane, and those
with innate physical weaknesses that render them for the
most part incompetent, it seems a safe estimate that 8
per cent of our population are far from having the capacities
of effective men and women, able, not merely to support
themselves, but really to push forward the world’s work.
The cost of caring for those who cannot care for themselves
because of their bad breeding is very heavy—perhaps two
hundred million or more a year. A study of the cause of
the increase of dependents indicates that it is because the
birth rate of the better classes is constantly falling; a Har-
vard class does not reproduce itself and at the present rate,
one thousand graduates of today will have only fifty descend-
ants two hundred years hence. On the other hand, recent
immigrants and the less effective descendants of the earlier
immigrants still continue to have large families; so that
from one thousand Roumanians today in Boston, at the
present rate of breeding, will come a hundred thousand two
hundred years hence to govern the fifty descendants of
Harvard’s sons! Such facts as these have awakened the
people to a sense of the omnipotence of human breeding.

The other impulse is the spread of knowledge of the
modern principles of heredity; and an appreciation of the
facts, first, that they afford a clear method in detail for
improving the blood of the nation, and, secondly, that the
results of this study can be set forth so simply and clearly
that they may become a part of our social idealism and may
serve to point the way to useful legislation. Heredity will
save the people from the perdition that is to come.

The realization of this fact has led to activity in various
directions. In Germany, an International Society of Race

310 Heredity and Eugenics

Hygiene has been organized and in England exists a Eugen-
ics Education Society which publishes the Eugenics Review,
and is organizing an International Congress of Eugenics for
1912. The Eugenics Education Society has fostered the for-
mation of several branches in the United Kingdom. For
some years Francis Galton maintained a Eugenics Labo-
ratory, directed by Professor Karl Pearson, that has pub-
lished a valuable Treasury of Human Inheritance, and was
lately well endowed at his death.

In America one of the first undertakings in Eugenics
was that of Dr. Alexander Graham Bell, who was much
impressed by the consequences of marriages of the deaf in
America. He founded the Volta Bureau in Washington,
which contains extensive records of the deaf.

In 1881 Mr. Loring Moody, of Boston, who was the
organizer of the Association for the Prevention of Cruelty
to Children and assisted in the foundation of the Asso-
ciation for the Prevention of Cruelty to Animals, organized
an Institute of Heredity, but his death soon after brought
his plans to naught.

In October, 1910, there was started at Cold Spring
Harbor on Long Island, the Eugenics Record Office, which
seeks to be a clearing-house for data on human blood lines
in America. It has collected several hundred records of
family traits and made extensive studies into the pedigrees
of the feeble-minded, epileptic, paupers, and insane. This
office is publishing a Bulletin. In time we shall have there,
we expect, data that will be useful to those contemplating
marriage. In various directions we hope to play an impor-
tant part in creating a sentiment and a knowledge that
shall lead to the improvement of the blood of the American

people.

INDEX

INDEX

Albinism, 278
Alcoholism, 285
Amphibians, 211
Appetency, 10
Ascaris, 45

Bacteria, work with, 202

Bateson, W., work of, 170

Beetles, work with, 181, 213, 216

Biffen, R. H., work of, 124

Bigelow, Mabel, pedigree of, 302

Bigelow, Melville M., pedigree of, 302

Biometry, 16

Breckinridge, Robert, Col., pedigree of,
304

Brown, John, Rev., pedigree of, 304

Buchanan, R. E., work of, 203

Burbank, Luther, work of, 130

Capsella, work with, 203

Carman, E. S., work of, 130

Carow, Edith Kermit, pedigree of, 302

Castle, William E., 39, 62; work of,
112, 149

Characters, coupled and antagonistic,

tor; nulliplex, 271; positive, nega-
tive, duplex, 270

Chickens, work with, 146

Chromatin, 26

Chromosomes, 26, 45, 66, 287

Churchill, Winston, pedigree of, 302

Citrus fruit, work with, 128

Clay, Henry, pedigree of, 304

Correns, C. E., work of, 41

Coulter, John M., 3, 22

Cuénot, work of, 65

Custis, George Washington
pedigree of, 303

Cytoplasm, 2

Parke,

Daphnia, work with, 210

Darwin, Charles, work of, 39, 142, 168

Darwin, Erasmus, 9

Davenport, C. E., 269, 289; work of,
149

Davis, B. M., work of, 199

Deaf-mutism, 280

Dementia, 283

Deming, Elizabeth, pedigree of, 302

Determiner, 269; absence of, 279

DeVries, Hugo, work of, 41, 170

Dihybrids, 93

Dominance, 105

Drosophila, work with, 75, 213

Dwight, Sereno Edwards, pedigree of,
301

Dwight, Theodore William, pedigree of,
302

Dwight, Timothy, pedigree of, 301

East, Edward Murray, 83, 113

Edwards, Jonathan, pedigree of, 301

Edwards, Richard, pedigree of, 301

Edwards, Timothy, pedigree of, 301

Egg, 31, 45

Emerson, R. A., work of, 101

Environment, 9

Epilepsy, 282

Eugenics, 269, 286; geography of man
in relation to, 289; organization of
movement, 308; in relation to migra-
tions, 294

Evolution, conception of, 4; explana-
tion of, 7; fact of, 5; method of, 30;

Eyes, inherited characters, 270, 276

Feeble-mindedness, 280
Fitzhugh, William Col., pedigree of,
393

314

Gager, C. S., work of, 205, 208, 222

Galton, F°., work of, 16

Gametes, 29, 62, 87, 141

Gametophyte, 34

Gates, Merrill Edward, pedigree of, 302

Gates, R. R., work of, 199

Genetics, 83

Genotype, r10

Geography, in relation to eugenics, 289

Germ plasm, 141; direct modification
of, 165; influence of the single, 300;
sudden transmutation in, 167

Goethe, work of, 9

Guinea-pigs, work with, 42, 149

Guthrie, C. G., work of, 146

Hair, characters of, 272

Henry, Patrick, pedigree of, 304

Heredity, 17, 42, 289; and sex, 62

Heterozygote, 62

Heydt, Hans Jorst, pedigree of, 298

Homozygote, 62

Howard, Benjamin, pedigree of, 304

Hoyt, Simeon, pedigree of, 297

Human breeding, relations of barriers
to, 289

Hybridization, 118

Hybrids, 91, 122, 166

Inheritance, 42, 83, 141; sex-limited,
287

Insanity, 283

Insects, work with, 212

Ishmaelites, the, pedigree of, 307

Johannsen, W. L., work of, 85, 110
Jukes, the, pedigree of, 305

Kammerer, work of, 211

Kentucky aristocracy, pedigree of, 304
Klebs, G., work of, 204

Knight, Thomas, work of, 84
Kolreuter, work of, 84

Lamarck, work of, to
Latency, 97
Lee, Francis Lightfoot, pedigree of, 303

Heredity and Eugenics

Lee, Richard, pedigree of, 303

Lee, Richard Henry, pedigree of, 303
Lee, Robert E., pedigree of, 303
Leptinotarsa, work with, 181, 216
Lutz, work of, 213

MacDougal, D. T., work of, 205, 222

Macro-gamete, 64

Maize, work with, 54, 85, 116

Man, inheritance of physical
mental traits of, 269

Manhattan Island and eugenics, 296

Mendel, Gregor, work of, 18, 40

Mendelism, 18, 40, 85, 100, 104

Mice, work with, 212

Micro-gamete, 64

Migrations, and their eugenic signifi-
cance, 294

Minot, Charles Sedgwick, pedigree of,
302

Monohybrids, 91

Morgan, T. H., work of, 75, 222

Mutation, 13, 170

and

Naegeli, Karl, work of, 40
Natural selection, 11
Neo-Darwinians, 168

Nereis, work with, 47

New England and eugenics, 296
Nitrogen, in soil, 120

Nucleus, 24

Oenothera, work with, 172, 197
Oranges, work with, 128
Orthogenesis, 14

Orton, W. A., work of, 125

Paine, Robert Treat, pedigree of, 302
Pangenesis, 142

Parthenogenesis, 67

Patton, Elizabeth, pedigree of, 304
Pauperism, 285

Pearson, Karl, work of, 16
Phosphorus, in soil, 120

Plant breeding, 113

Potassium, in soil, 120

Index

Preston, John, pedigree of, 304
Price, H. L., work of, 125
Pringsheim, N., work of, 203
Protoplast, 2

Punnett, R. C., work of, 66

Reeve, Sarah Tapping, pedigree of, 301

Reichert, work of, 22

Reproduction, power of, 23; sexual, 29;
by spores, 29

Richardson, Ann, pedigree of, 302

Riley, C. V., work of, 65

Russo, work of, 65

St. Hilaire, Geoffrey, work of, 9

Saltation, 171

Schenk, work of, 65

Sedgwick, Catherine Maria, pedigree of,
302

Selection, 118, 131

Sempervivum, work with, 204

Sex, and heredity, 62; immorality, 285

Shamel, A. D., work of, 124

Skeleton, inherited characters of, 277

Soil, 120

Sparks, Jared, pedigree of, 301

Sperm, 31, 45

Sporophyte, 34

Stoughton, Abigail, pedigree of, 302

Sumner, F. B., work of, 210, 212

Swimming spores, 29

Synthesis of a mutating race, 182

Talcott, Mary, pedigree of, 301
Thomsen’s disease, 278
Tobacco, work with, 114
Tower, William Lawrence, 148
Treat, Mary, work of, 65

315

Tschermak, E., work of, 41
Tuttle, Elizabeth, pedigree of, 300
Tyler, Daniel, pedigree of, 301

Unit-character, 48
Use and disuse, to

Variation, germinal in animals, 210;
in Chrysomelid beetles, 213; by com-
bined selection and hybridization,

different forces, 200; by

origin of, 144;

234; by
hybridization, 231;
peripheral origin of, 143; in plants,
202; by selection, 238; somatic,
145

Vilmorin, P., work of, 84

Vincent, Marvin Richardson, pedigree
of, 302

Virginia and eugenics,
families, of 303

Von Riimker, work of, 125

295; + first

Waite, Morrison, pedigree of, 302

Washington, George, pedigree of, 304

Webber, H., work of, 125, 128

Weismann, A., work of, 41, 110, 168

Whitney, Henrietta Frances, pedigree
of, 302

Wilson, E. B., work of, 47

Woltereck, work of, 210

Woolsey, Theodore Dwight, pedigree
of, 301

Yeasts, work with, 202
Zedebauer, E., work of, 203

Zoospore, 209
Zygote, 30, 62

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