AMEBOID MOVEMENT
AMEBOID MOVEMENT
BY
ASA A. SCHAEFFER, PH.D.
PROFESSOR OF ZOOLOGY, UNIVERSITY
OF TENNESSEE
PRINCETON UNIVERSITY PRESS
PRINCETON
LONDON: HUMPHREY MILFORD
OXFORD UNIVERSITY PRESS
1920
Copyright, 1920, by
PRINCETON UNIVERSITY PRESS
Published 1920
Printed in the United States of America
[Illustration]
PREFACE
Although the subject of ameboid movement is discussed in this book
chiefly because of its intrinsic interest, yet the interests of the
student of medicine, the psychologist, the physiologist, the
evolutionist and the general biologist have constantly been kept in
mind. For the medical investigator probably finds no better means of
approach to the study of the reactions and especially the movements of
the white blood corpuscles, which play such an important part in the
economy of the human body, than the ameba; white blood corpuscles and
amebas are strikingly similar in many characteristics and in the
fundamental processes of the movement they are probably identical. The
comparative psychologist is keenly interested in the activities of the
ameba because it exhibits to him the operation of the animal mind in its
greatest simplicity. To the physiologist ameboid movement has for a long
time represented the simplest phase of muscular contraction as it is
known in the vertebrates. The philosophical evolutionist sees in the
ameba, both in its structure and in its activities, a close
approximation to the earliest ancestor of the animals. And the general
biologist, aside from his usual interest in the properties of living
matter wherever it may be found, is especially interested in discovering
how many of the activities of the ameba are common to other organisms.
But in addition to presenting an account of the main facts concerned in
the movement of the ameba from the various points of view mentioned
above, this book has a second object which is scarcely subsidiary to the
main one. This second object is to present the thesis that moving
organisms in which orienting organs are absent or not functioning,
always move in orderly paths, i. e., in helical or true spiral paths.
The movements of the ameba under controlled conditions, which, as the
following pages will show, take the form of a helical spiral projected
on a plane surface, therefore serve as an introductory study to the
movements of organisms generally. For the presumption is strong that
there is an innate tendency in all organisms that move which compels
them, when free from stimulation, to move in definite predictable paths.
This thesis is discussed at some length in Chapters XII and XIII.
In view of the fact that ameboid movement has been considered largely as
a theoretical question heretofore, I wish to state at once that my
discussion of this subject is based directly on observation and
experiment. I have no new theory of ameboid movement to offer; the list
of theories is already extensive enough. I am, on the other hand,
strongly of the opinion that this fundamental question, if it is to be
solved at all, can be solved only by persistent observation and
experiment on the ameba and related organisms themselves. “All knowledge
is vain and erroneous excepting that brought into the world by sense
perception, the mother of all certainty” (Leonardo).
CONTENTS
PAGE
CHAPTER I
Introduction 1
CHAPTER II
Historical Sketch 3
CHAPTER III
The General Features of Endoplasmic Streaming 8
CHAPTER IV
The Transformation of Endoplasm into Ectoplasm 18
CHAPTER V
Pseudopods and the Nature of the Ectoplasm 25
CHAPTER VI
The Species Question 41
CHAPTER VII
Experiments on the Surface Layer of the Ameba 48
CHAPTER VIII
On the Nature of the Surface Layer 63
CHAPTER IX
The Surface Layer and Theories of Ameboid Movement 76
CHAPTER X
Streaming, Contractility and Ameboid Movement 92
CHAPTER XI
The Surface Layer as a Locomotor Organ 105
CHAPTER XII
The Wavy Path of the Ameba 109
CHAPTER XIII
The Wavy Path of the Ameba and the Spiral Paths of
Ciliates and Other Organisms 126
CHAPTER XIV
Conclusions 142
Bibliography 146
CHAPTER I
INTRODUCTION
The manner of movement common to amebas has attracted the attention of
biologists ever since the discovery of ameba by Rösel v. Rosenhof in
1755. In his description of “Der kleine Proteus” he records the
observation that the various form changes which the ameba undergoes are
associated with the streaming of the endoplasm. This observation marks
the very beginning of the investigation of ameboid movement. And this
investigation also possesses the distinction of being the most important
single observation that has thus far been recorded in this special
field, for it is now generally understood that by ameboid movement is
meant movement due to the streaming of protoplasm.
The phenomenon of ameboid movement as discovered by v. Rosenhof, was an
isolated phenomenon. It attracted attention mainly because of its
uniqueness, for it was the only instance of the kind that was then
known. It could not be compared with any other form of movement; and the
animal itself, considered apart from the streaming of the protoplasm,
was unique also, because of its remarkable form changes which it alone,
of all the animals then known, exhibited.
But when Corti in 1774 discovered streaming protoplasm in the cells of
chara and various other plants, the ameba could no longer be said to
occupy this position of isolation. Although streaming is not accompanied
by locomotion in chara, it had been observed that movement in the ameba
was always accompanied by streaming, so it came to be generally accepted
that the really fundamental feature of ameboid movement was the
streaming of the protoplasm.
The ameba came to be of especial interest to the physiologists later on
when the finer structures of the larger animals were studied more
carefully. Thus when the normal movements of the white blood corpuscles
were discovered, no one failed to be struck with their ameboid
characteristics in almost every detail of movement, feeding habits and
gross structure. The great importance of the functions that have been
ascribed to leukocytes, and their very widespread occurrence in the
higher animals has served to give rise to the belief that ameboid
characteristics were not unique among animals, but common to many of
them. The discovery of ameboid movements among plant zoospores, among
animal ova, in the endoderm cells lining the digestive tract of a great
variety of animals, in the nuclei of some animal cells, in the wandering
cells of sponges and other animals--all these instances of ameboid
movement occurring in such widely different tissues inevitably placed it
among the most important phenomena known to occur in organisms.
Out of the discovery that ameboid movement may be exhibited in some form
or other in so many different kinds of organisms, grew the theory that
even muscular movement as known in man and the higher animals is at
bottom a specialized sort of ameboid movement; not merely
phylogenetically, but as it is now known. As we shall see however in the
following pages, this theory of muscular movement cannot be based
specifically on the streaming process per se, but it is very probable,
on the other hand, that the same process which underlies contraction of
the ectoplasm in the ameba also underlies contraction in muscular
tissue.
But this remarkable story of the development of a single unrelated
observation into a widespread biological phenomenon is not yet complete.
With its further development the following pages are concerned. It will
be shown that the movement of the surface film of the ameba is analogous
to that of some blue-green algae, diatoms and crawling euglenas, in
which organisms the surface film seems to be the vehicle of movement.
Thus the ameba finds itself related to these organisms by new ties. More
important still is the significance of the wavy path of the ameba, which
may possibly be due to the same fundamental mechanism that controls,
under suitable conditions, the direction of the path in man and many
other animals and motile plant cells. Thus the phenomenon of ameboid
movement born in nakedness and utter isolation, has become attired, in a
brief space, with the Victorian garb of a Fundamental.