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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
PREFACE
Although the subject of ameboid movement is discussed in this bookchiefly because of its intrinsic interest, yet the interests of thestudent of medicine, the psychologist, the physiologist, theevolutionist and the general biologist have constantly been kept inmind. For the medical investigator probably finds no better means ofapproach to the study of the reactions and especially the movements ofthe white blood corpuscles, which play such an important part in theeconomy of the human body, than the ameba; white blood corpuscles andamebas are strikingly similar in many characteristics and in thefundamental processes of the movement they are probably identical. Thecomparative psychologist is keenly interested in the activities of theameba because it exhibits to him the operation of the animal mind in itsgreatest simplicity. To the physiologist ameboid movement has for a longtime represented the simplest phase of muscular contraction as it isknown in the vertebrates. The philosophical evolutionist sees in theameba, both in its structure and in its activities, a closeapproximation to the earliest ancestor of the animals. And the generalbiologist, aside from his usual interest in the properties of livingmatter wherever it may be found, is especially interested in discoveringhow many of the activities of the ameba are common to other organisms.
But in addition to presenting an account of the main facts concerned inthe movement of the ameba from the various points of view mentionedabove, this book has a second object which is scarcely subsidiary to themain one. This second object is to present the thesis that movingorganisms 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 thefollowing pages will show, take the form of a helical spiral projectedon a plane surface, therefore serve as an introductory study to themovements of organisms generally. For the presumption is strong thatthere is an innate tendency in all organisms that move which compelsthem, 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 asa theoretical question heretofore, I wish to state at once that mydiscussion of this subject is based directly on observation andexperiment. I have no new theory of ameboid movement to offer; the listof theories is already extensive enough. I am, on the other hand,strongly of the opinion that this fundamental question, if it is to besolved at all, can be solved only by persistent obser