Transcriber's note: A few typographical errors have been corrected: they
are listed at the end of the text.
Text enclosed by underscores is in italics (_italics_).
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following the carat is superscripted (example: X^1). Similarly an
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* * * * *
THE
ORIGIN OF VERTEBRATES
BY
WALTER HOLBROOK GASKELL
M.A., M.D. (CANTAB.), LL.D. (EDIN. AND McGILL UNIV.); F.R.S.; FELLOW OF
TRINITY HALL AND UNIVERSITY LECTURER IN PHYSIOLOGY, CAMBRIDGE; HONORARY
FELLOW OF THE ROYAL MEDICAL AND CHIRURGICAL SOCIETY; CORRESPONDING MEMBER
OF THE IMPERIAL MILITARY ACADEMY OF MEDICINE, ST. PETERSBURG, ETC.
LONGMANS, GREEN, AND CO.
39 PATERNOSTER ROW, LONDON
NEW YORK, BOMBAY, AND CALCUTTA
1908
_All rights reserved_
CONTENTS
PAGE
INTRODUCTION 1
CHAPTER I
THE EVIDENCE OF THE CENTRAL NERVOUS SYSTEM
Theories of the origin of vertebrates--Importance of the central
nervous system--Evolution of tissues--Evidence of Palæontology--
Reasons for choosing Ammocoetes rather than Amphioxus for the
investigation of this problem--Importance of larval forms--
Comparison of the vertebrate and arthropod central nervous
systems--Antagonism between cephalization and alimentation--
Life-history of lamprey, not a degenerate animal--Brain of
Ammocoetes compared with brain of arthropod--Summary 8