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                    YALE UNIVERSITY

        MRS. HEPSA ELY SILLIMAN MEMORIAL LECTURES


                  PROBLEMS OF GENETICS

              SILLIMAN MEMORIAL LECTURES
          PUBLISHED BY YALE UNIVERSITY PRESS

  ELECTRICITY AND MATTER. _By_ JOSEPH JOHN THOMSON,
    D.SC., LL.D., PH.D., F.R.S., _Fellow of Trinity College,
    Cambridge, Cavendish Professor of Experimental Physics, Cambridge_.
  _Price $1.25 net; postage 10 cents extra._

  THE INTEGRATIVE ACTION OF THE NERVOUS SYSTEM.
    _By_ CHARLES S. SHERRINGTON,
     D.SC., M.D., HON. LL.D., TOR., F.R.S.,
    _Holt Professor of Physiology in the University of Liverpool_.
  _Price $3.50 net; postage 25 cents extra._

  RADIOACTIVE TRANSFORMATIONS. _By_ ERNEST RUTHERFORD,
    D.SC., LL.D., F.R.S., _Macdonald Professor of Physics,
    McGill University_.
  _Price $3.50 net; postage 22 cents extra._

  EXPERIMENTAL AND THEORETICAL APPLICATIONS OF
      THERMODYNAMICS TO CHEMISTRY.
  _By_ DR. WALTHER NERNST, _Professor and Director of the
    Institute of Physical Chemistry in the University of Berlin_.
  _Price $1.25 net; postage 10 cents extra._

  THE PROBLEMS OF GENETICS. _By_ WILLIAM BATESON, M.A.,
    F.R.S., _Director of the John Innes Horticultural Institution,
    Merton Park, Surrey, England_.
  _Price $4.00 net; postage 25 cents extra._

  STELLAR MOTIONS.
    WITH SPECIAL REFERENCE TO MOTIONS DETERMINED BY MEANS OF
    THE SPECTROGRAPH. _By_ WILLIAM WALLACE CAMPBELL, SC.D., LL.D.,
   _Director of the Lick Observatory, University of California_.
  _Price $4.00 net; postage 30 cents extra._

  THEORIES OF SOLUTIONS. _By_ SVANTE AUGUST ARRHENIUS,
    PH.D., SC.D., M.D., _Director of the Physico-Chemical
    Department of the Nobel Institute, Stockholm, Sweden_.
  _Price $2.25 net; postage 15 cents extra._

  IRRITABILITY.
       A PHYSIOLOGICAL ANALYSIS OF THE GENERAL EFFECT OF
       STIMULI IN LIVING SUBSTANCES.
    _By_ MAX VERWORN,
    _Professor at Bonn Physiological Institute_.
  _Price $3.50 net; postage 20 cents extra._

  THE EVOLUTION OF MODERN MEDICINE.
    _By_ SIR WILLIAM OSLER, BART., M.D., LL.D., SC.D.,
    _Regius Professor of Medicine, Oxford University_.
  _Price $3.00 net; postage 40 cents extra._




                     PROBLEMS OF GENETICS

                              BY
                 WILLIAM BATESON, M.A., F.R.S.

        DIRECTOR OF THE JOHN INNES HORTICULTURAL INSTITUTION,
            HON. FELLOW OF ST. JOHN'S COLLEGE, CAMBRIDGE,
        AND FORMERLY PROFESSOR OF BIOLOGY IN THE UNIVERSITY

                     _WITH ILLUSTRATIONS_

                         [Illustration]

                NEW HAVEN: YALE UNIVERSITY PRESS
                    LONDON: HUMPHREY MILFORD
                     OXFORD UNIVERSITY PRESS

                             MCMXIII


                         Copyright, 1913
                       By YALE UNIVERSITY

                First printed August, 1913, 1000 copies


[** Transcriber's Note:
     Underscores "_" before and after a word or phrase indicate ITALICS
       in the original text.
     Hyphenation was used inconsistently by the author and has been
        left as in the original text. ]




                    THE SILLIMAN FOUNDATION

In the year 1883 a legacy of about eighty-five thousand dollars was left
to the President and Fellows of Yale College in the city of New Haven,
to be held in trust, as a gift from her children, in memory of their
beloved and honored mother, Mrs. Hepsa Ely Silliman.

On this foundation Yale College was requested and directed to establish
an annual course of lectures designed to illustrate the presence and
providence, the wisdom and goodness of God, as manifested in the natural
and moral world. These were to be designated as the Mrs. Hepsa Ely
Silliman Memorial Lectures. It was the belief of the testator that any
orderly presentation of the facts of nature or history contributed
to the end of this foundation more effectively than any attempt to
emphasize the elements of doctrine or of creed; and he therefore
provided that lectures on dogmatic or polemical theology should be
excluded from the scope of this foundation, and that the subjects should
be selected rather from the domains of natural science and history,
giving special prominence to astronomy, chemistry, geology, and anatomy.

It was further directed that each annual course should be made the basis
of a volume to form part of a series constituting a memorial to Mrs.
Silliman. The memorial fund came into the possession of the Corporation
of Yale University in the year 1901; and the present volume constitutes
the fifth of the series of memorial lectures.




                           PREFACE

This book gives the substance of a series of lectures delivered in Yale
University, where I had the privilege of holding the office of Silliman
Lecturer in 1907.

The delay in publication was brought about by a variety of causes.

Inasmuch as the purpose of the lectures is to discuss some of the wider
problems of biology in the light of knowledge acquired by Mendelian
methods of analysis, it was essential that a fairly full account of
the conclusions established by them should first be undertaken and I
therefore postponed the present work till a book on Mendel's Principles
had been completed.

On attempting a more general discussion of the bearing of the phenomena
on the theory of Evolution, I found myself continually hindered by the
consciousness that such treatment is premature, and by doubt whether
it were not better that the debate should for the present stand
indefinitely adjourned. That species have come into existence by an
evolutionary process no one seriously doubts; but few who are familiar
with the facts that genetic research has revealed are now inclined to
speculate as to the manner by which the process has been accomplished.
Our knowledge of the nature and properties of living things is far too
meagre to justify any such attempts. Suggestions of course can be made:
though, however, these ideas may have a stimulating value in the lecture
room, they look weak and thin when set out in print. The work which may
one day give them a body has yet to be done.

The development of negations is always an ungrateful task apt to be
postponed for the positive business of experiment. Such work is happily
now going forward in most of the centers of scientific life. Of many
of the subjects here treated we already know more than we did in 1907.
The delay in production has made it possible to incorporate these new
contributions.

The book makes no pretence at being a treatise and the number of
illustrative cases has been kept within a moderate compass. A good many
of the examples have been chosen from American natural history, as being
appropriate to a book intended primarily for American readers. The facts
are largely given on the authority of others, and I wish to express my
gratitude for the abundant assistance received from American colleagues,
especially from the staffs of the American Museum in New York, and of
the Boston Museum of Natural History. In connexion with the particular
subjects personal acknowledgments are made.

Dr. F. M. Chapman was so good as to supervise the preparation of the
 Plate of _Colaptes_, and to authorize the loan of the Plate
representing the various forms of _Helminthophila_, which is taken from
his _North American Warblers_.

I am under obligation to Messrs. Macmillan & Co., for permission to
reproduce several figures from _Materials for the Study of Variation_,
illustrating subjects which I wished to treat in new associations, and
to M. Leduc for leave to use Fig. 