CHAPTER I 

 INTRODUCTION 



The manner of movement common to amebas has attracted 

 the attention of biologists ever since the discovery of ameba by 

 Rosel 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 ob- 

 servation 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, be- 

 cause 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 stream- 

 ing, so it came to be generally accepted that the really fundamental 

 feature of ameboid movement was the streaming of the proto- 

 plasm. 



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 



