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 psychol- 

 ogist 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 com- 

 mon to other organisms. 



But in addition to presenting an account of the main facts con- 

 cerned 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 pre- 

 sent 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 sur- 

 face, therefore serve as an introductory study to the movements 

 of organisms generally. For the presumption is strong that there 



