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81

Observations on the Spinal Cord of the Emu and its Segmen

tation. By IRVING HARDESTY. (From the Hearst Anat-
omical Laboratory of the University of California.) With

four figures.
The Selection of Random Movements as a Factor in Phototaxis.

By S. J. HOLMES. (From the Zoological Laboratory of

the University of Michigan.)
Notes on the Development of the Sympathetic Nervous System

in the Common Toad. By WALTER C. JONES, M.D.
With twelve figures.

98

113

Editorial

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132

Concerning the Genetic Relations of Types of Action.
The Basis for Taxis and Certain Other Terms in the Be-

havior of Infusoria.
The Problem of Instinct.

138

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.

144

A Review of Some Recent Literature on the Chemistry of the

Central Nervous System. By ISADOR H. CORIAT.
Worcester Insane Hospital.

148

Literary Notices.

160

THE JOURNAL OF COMPARATIVE NEUROLOGY AND PSY. CHOLOGY is published bi-monthly. The annual volume of six numbers comprises about 500 pages, with plates and text-figures. The subscription price is $4.00 a year, strictly net (foreign subscription, $4.30, 18 s., M. 18, 22 fr., L. 22), postage prepaid.

Authors receive 50 reprints of their papers gratis and additional copies are supplied at cost. All MSS. and matter for review relating to the Structure of the Nervous System and all business correspondence should be addressed to the MANAGING EDITOR AT DENISON UNIVERSITY, GRANVILLE, Ohio. Editorial Matter relating to Comparative Psychology and the Physiology of the Nervous System should be sent directly to DR. ROBERT M. YERKES, PSYCHOLOGICAL LABORATORY, HARVARD UNIVERSITY, CAMBRIDGE, Mass.

Entered a second-claw mattar in bo postalo at Gnaville, 0.

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ASSOCIATED WITH
OLIVER S. STRONG,

HERBERT S. JENNINGS,
Columbia University

University of Pennsylvania

COLLABORATORS

J. MARK BALDWIN, Johns Hopkins University
FRANK W. BANCROFT, University of California
LEWELLYS F. BARKER, University of Chicago
H. HEATH BAWDEN, Vassar College
ALBRECHT BETHE, University of Strassburg
G. E COGHILL, Pacific University
FRANK J. COLE, University of Liverpool
H. E, CRAMPTON, Columbia University
O. B. DAVENPORT, University of Chicago
WM, HARPER DAVIS, Lehigh University
HENRY H. DONALDSON, University of Chicago
LUDWIG EDINGER, Frankfurt a-M.
8. I. FRANZ, McLean Hospital, Waverley, Mass.
THOMAS H. HAINES, Ohio State University
A. VAN GEHUCHTEN, University of Louvain
R. G. HARRISON, Johns Hopkins University
C. F. HODGE, Clark University
8. J. HOLMES, University of Michigan
EDWIN B. HOLT, Harvard University
G. CARL HUBER, University of Michigan
JOSEPH JASTROW, University of Wisconsin
J. B. JOHNSTON, West Virginia University

B. F. KINGSBURY, Cornell University
FREDERIC S. LEE, Columbia University
JACQUES LOEB, University of California
E. P. LYON, St. Louis University
ADOLF MEYER, N. Y. State Pathological Inst.
THOS. H. MONTGOMERY, Jr., Univ. of Texas
WESLEY MILLS, McGill University
C. LLOYD MORGAN, University Collego, Bristol
T. H. MORGAN, Columbia 'Iniversity
A. D. MORRILL, Hamilton College
HUGO MUENSTERBERG, Harvard University
W. A. NAGEL, University of Berlin
G. H. PARKER, Harvard University,
STEWART PATON, Johns Hopkins University
RAYMOND PEARL, University of Michigan
C. W. PRENTISS, Western Reserve University
C. S. SHERRINGTON, University of Liverpool
G. ELLIOT SMITH, Gov't. Medical School, Cairo
EDWARD L. THORNDIKE, Columbia University
JOHN B. WATSON, University of Chicago
W. M. WHEELER, Am. Museum of Nat. History
C. O. WHITMAN, University of Chicago

Published bi-monthly
DENISON UNIVERSITY, GRANVILLE, OHIO

JOURNAL OF
COMPARATIVE NEUROLOGY AND PSYCHOLOGY.

On March 30th. last nearly all of the reserve copies of back numbers of this Journal were destroyed by fire. Of some issues we still have an abundant supply and these will be sold separately at no advance over former prices. Some of the issues, however, will be sold only in complete sets.

Only a very few complete sets remain, but the management has decided to offer these, as long as they last, at no advance over former prices, save that the purchaser will be expected to pay transportation charges. Volumes I to XV inclusive are offered for $53.50; and carriage will be prepaid to points in North America for 500 additional and to foreign countries in the Postal Union for $2.50 additional.

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Comparative Neurology and Psychology

Volume XV

1905

Number 3

THE MORPHOLOGY OF THE VERTEBRATE HEAD

FROM THE VIEWPOINT OF THE FUNCTIONAL
DIVISIONS OF THE NERVOUS SYSTEM.1

By J. B. JOHNSTON.

With Plates I to IV.

TABLE OF CONTENTS.

1.

a.

c.

2.

176 176 177 180 182 184 188 191 194 197 204 207

2II

Introduction.

Nature of the unsettled problems
b. Nerve components

Functional divisions of the nervous system
d. Bearing upon the subject of head morphology

Number and relations of mesodermic somites
3. Branchial apparatus and lateral musculature
4. Segmentation of the central nervous system
5. Typical sense organs of vertebrates
6. The anterior end of the head
7. The segment containing N. III. Segment 5
8. Segment 6
9. The absence of nerve roots from one or more hind brain segments and

the determination of the neuromeres concerned
Segment 7.

The acustico-lateral system
Segments 8 and following
The occipital region and the posterior limit of the head. The constitu-

tion of the vagus. Shifting of organs
13. The morphology of the visual organs
14. The nerves of Platt, Locy and Pinkus
15. Morphology of the olfactory organ. Functional and morphological

relations to the gustatory system 16. The first four head segments

Segment 4 b. Segment 3

Segment 2

d. Segment i Prostomium 17. The dorsal commissures of the brain

10.

215

II.

223

12.

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Studies from the Zoological Laboratory of West Virginia University, No.

5. 9,

257
238
260

18. The sympathetic system 19. Relation

dorsal and ventral nerve roots to the myotomes 20. Comparison of head and trunk Summary List of papers cited Description of figures

.

261 265

273

1. Introduction.

a. Nature of the unsettled problems. Shall we consider vertebrates as animals possessing a high degree of cephalization from their first appearace? The structure of their near relatives, Amphioxus and Ascidians, is against this view. The structural relations of vertebrates and invertebrates indicate that the ancestors of the vertebrates were segmented invertebrates in which the process of cephalization had not gone very far. Even within typical vertebrates evidence is not lacking that the special sense organs of the head were late to appear; that the branchial apparatus was at one time more extensive, reaching into what is now the trunk; that the nerves of the branchial region once had a more simple segmental arrangement; and that in the brain itself the several regions were once less highly specialized than at present. If Amphioxus be considered, the presence of true nephridia (41) in the head and the slight specialization in the head region seem to relate this "lowest vertebrate with invertebrates rather far down the scale.

If, then, the ancestral vertebrate had only a slight head development, it is evident that the interpretation of the special organs of the head of typical vertebrates is to be reached by a study of their structure, function, and phylogenetic history, with a view to tracing them back to their unspecialized beginnings. When each organ has thus been followed back to its ancestral condition we shall have reduced the vertebrate head to terms-not of the trunk, but of a more simple condition which underlies both head and trunk. Such is the real problem of head morphology as the writer understands it.

The central difficulty in framing such a conception of the head is the matter of segmentation. Head specialization has

1

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