4 AMEBOID MOVEMENT 



Jennings ('04), however, from extended study of the physi- 

 ology of the ameba, stressing especially movement and feeding, 

 denied that the transformation of endoplasm into ectoplasm, and 

 vice versa, is necessary or even of frequent occurrence during 

 movement. Instead of these transformations occurring regularly, 

 as Biitschli and Rhumbler described them, Jennings concluded 

 that the ectoplasm is more or less permanent, behaving like an 

 elastic skin, which rolls over and over as the ameba moves along. 

 The ectoplasm thus remains ectoplasm, and the endoplasm retains 

 its identity, for considerable periods of time, instead of being 

 continually transformed, the one into the other, as the ameba 

 moves along. 



Although observations with regard to movement in ameba have 

 consisted almost wholly of the mutual relations of ectoplasm and 

 endoplasm, it is important to note that the existence of a third 

 layer of protoplasm, outside of the ectoplasm, was foreshadowed 

 by an observation of Biitschli ('92, p. 219) while examining a 

 pelomyxa. To his great surprise he found that there were cur- 

 rents of water, as evidenced by the movement of suspended par- 

 ticles, at the sides and in close contact with the ectoplasm of the 

 pelomyxa, which flowed slowly forwards toward the anterior end. 

 No details were given and no explanation offered for the cause 

 of the currents excepting the suggestion that there might be a 

 thin skin over the animal, which moves slowly forward. 



Two years later Blochmann ('94) demonstrated by means of the 

 very fine cilia-like projections which frequently cover the out- 

 side of pelomyxas, that the surface of the pelomyxa actually 

 moves forward during active locomotion. He did not state de- 

 finitely whether or not he considered this surface as a part of 

 the ectoplasm. 



This observation of Blochmann was not developed, however, 

 until Jennings ('04), by means of particles attached to the outer 

 surface of amebas, studied the forward movement of this layer. 

 The results of Jennings' work led him to conclude that the outer 

 surface of amebas, which move forward as demonstrated by at- 

 tached particles of soot and other substances, is continuous with 

 the ectoplasm, and is really the ectoplasm. The rate of move- 

 ment of this layer was stated to be about the same as that of the 



