REGENERATION

BY
THOMAS HUNT MORGAN, Ph.D.
PROFESSOR OF BIOLOGY, BRYN MAWR COLLEGE

New York
THE MACMILLAN COMPANY
LONDON: MACMILLAN & CO., Ltd.
1901
All rights reserved

Copyright, 1901,
By THE MACMILLAN COMPANY.
Norwood Press
J. S. Cushing & Co.—Berwick & Smith
Norwood, Mass., U.S.A.

To My Mother

PREFACE

This volume is the outcome of a course of five lectures on “Regeneration and Experimental Embryology,” given in Columbia University in January, 1900. The subjects dealt with in the lectures are here more fully treated and are supplemented by the discussion of a number of related topics. During the last few years the problems connected with the regeneration of organisms have interested a large number of biologists, and much new work has been done in this field; especially in connection with the regenerative phenomena of the egg and early embryo. The development of isolated cells or blastomeres has, for instance, aroused widespread interest. It has become clearer, as new discoveries have been made, that the latter phenomena are only special cases of the general phenomena of regeneration in organisms, so that the results have been treated from this point of view in the present volume.

If it should appear that at times I have gone out of my way to attack the hypothesis of preformed nuclear germs, and also the theory of natural selection as applied to regeneration, I trust that the importance of the questions involved may be an excuse for the criticism.

If I may be pardoned a further word of personal import, I should like to add that it has seemed to me that far more essential than each special question with which the biologist has to deal is his attitude toward the general subject of biology as a science. Never before in the history of biology has this been more important than at the present time, when we so often fail to realize which problems are really scientific and which methods are legitimate for the solution of these problems. The custom of indulging in exaggerated and unverifiable speculation bids fair to dull our appreciation for hypotheses whose chief value lies in the possibility of their verification; but those who have spent their time and their imagination in such speculations cannot hope for long to hold their own against the slow but certain advance of a scientific spirit of investigation of organic phenomena. The historical questions with which so many problems seem to be connected, and for which there is no rigorous experimental test, are perhaps responsible for the loose way in which many problems in biology are treated, where fancy too often supplies the place of demonstration. If, then, I have tried to use my material in such a way as to turn the evidence against some of the uncritical hypotheses of biology, I trust that the book may have a wider bearing than simply as a treatment of the problems of regeneration.

I wish to acknowledge my many obligations to Professor H. F. Osborn and to Professor E. B. Wilson for friendly criticism and advice; and in connection with the revision of the text I am greatly indebted to Professor J. W. Warren, to Professor W. M. Wheeler, to Professor G. H. Parker, and to Professor Leo Loeb.

Bryn Mawr College, Pennsylvania,
June 11, 1901.

CONTENTS

[CHAPTER I
General Introduction]
PAGE
Historical Account of the Work on Regeneration of Trembley, Bonnet, and Spallanzani[1]
Some Further Examples of Regeneration[6]
Definition of Terms[19]
[CHAPTER II
The External Factors of Regeneration in Animals]
The Effect of Temperature[26]
The Effect of Food[27]
The Effect of Light[29]
The Effect of Gravity[30]
The Effect of Contact[33]
The Effect of Chemical Changes in the Environment[35]
General Conclusions[36]
[CHAPTER III
The Internal Factors of Regeneration in Animals]
Polarity and Heteromorphosis[38]
Lateral Regeneration[43]
Regeneration from an Oblique Surface[44]
The Influence of Internal Organs at the Cut-surface[52]
The Influence of the Amount of New Material[54]
The Influence of the Old Parts on the New[62]
The Influence of the Nucleus on Regeneration[65]
The Closing in of Cut-edges[69]
[CHAPTER IV
Regeneration in Plants]
Regeneration in Flowering Plants[71]
Regeneration in Liverworts, Mosses, and Moulds[84]
Hypothesis of Formative Stuffs[88]
[CHAPTER V
Regeneration and Liability to Injury]
Examples of Supposed Connection between Regeneration and Liability to Injury[92]
Regeneration in Different Parts of the Body[97]
Regeneration throughout the Animal Kingdom[103]
Regeneration and the Theory of Natural Selection[108]
[CHAPTER VI
Regeneration of Internal Organs. Hypertrophy. Atrophy]
Regeneration of Liver, Eye, Kidney, Salivary Glands, Bones, Muscles, Nerves, Brain, and Cord of Vertebrates[111]
Examples of Hypertrophy[115]
Theories of Hypertrophy[118]
Atrophy[123]
Incomplete Regeneration[125]
[CHAPTER VII
Physiological Regeneration]
Supposed Relation between Physiological Regeneration and Restorative Regeneration[128]
Regeneration and Growth[131]
Double Structures[135]
[CHAPTER VIII
Self-division and Regeneration. Budding and Regeneration. Autotomy. Theories of Autotomy]
Review of Groups in which Self-division occurs[142]
Division in Plane of Least Resistance[144]
Review of Groups in which Budding occurs. Relation of Budding to Regeneration[149]
Autotomy[150]
Theories of Autotomy[155]
[CHAPTER IX
Grafting and Regeneration]
Examples of Grafting in Hydra, Tubularia, Planarians, Earthworms, Tadpoles[159]
Grafting Pieces of Organs in Other Parts of the Body in Higher Animals[178]
Grafting of Parts of Embryos of the Frog[182]
Union of Two Eggs to form One Embryo[188]
[CHAPTER X
The Origin of New Cells and Tissues]
Origin of New Cells in Annelids[190]
Origin of the New Lens in the Eye of Salamanders[203]
The Part played by the “Germ-layers” in Regeneration[207]
The Supposed Repetition of Phylogenetic and Ontogenetic Processes in Regeneration[212]
[CHAPTER XI
Regeneration in Egg and Embryo]
Introduction[216]
Regeneration in Egg of Frog[217]
Regeneration in Egg of Sea-urchin[228]
Regeneration in Other Forms: Amphioxus, Ascidian, Ctenophore, Snail, Jelly-fish, Fish[236]
[CHAPTER XII
Theories of Development]
Theories of Isotropy and of Totipotence of Cells[242]
Theory of Qualitative Division of Nucleus[243]
Theory of Equivalency of Cells[244]
Theory of the Organized Structure of the Protoplasm[246]
Theory of Cells as Units[250]
Further Analysis of Theories of Qualitative Nuclear Divisions and of the Equivalency of Blastomeres[252]
Driesch’s Analytical Theory, Criticism, and Later Theories of Driesch[253]
Conclusions[256]
[CHAPTER XIII
Theories of Regeneration]
Pre-formation Theory[260]
Comparison with Growth of Crystal[263]
Completing Theory[264]
Theory of Formative Stuffs[265]
Conclusions[269]
Theory of Tensions controlling Growth[271]
[CHAPTER XIV
General Considerations and Conclusions]
Organization[277]
Machine Theory of Development and of Regeneration[283]
Teleology[283]
“Action at a Distance”[284]
Definition of Terms: Cause, Stimulus, Factor, Force, Formative Force, Organization[287]
Regeneration as a Phenomenon of Adaptation[288]
[Literature][293]
[Index][311]