ON THE FEEDING HABITS OF AMEBA 543 



sweise der Amobe hervorzurufen geeignet ist. Das Amobenplasma 

 schickt namlich an beiden Seiten der Beute vorbei Pseudopodien, die 

 sieh jenseits der Beuto miteinander vcreinigen, nach ihrer Verschmcl- 

 zimg einen vollstandigen Wall um sie herum bilden, und sich bald 

 darauf aueh aiif der Ober- und Unterseite der Amobe zusammenschliessen, 

 so dass die Beute vollstandig eingekerkert wird, ohne dass das Plasma 

 selbst bis dahin mit ihr irgendwo in direkten Kontakt gekommen zu sein 

 braucht (Fig. 1). Soweit es sich hierbei umlebende Beutckorper han- 

 delt, sieht diese Art des Nahrungserwerbes einer Uberlistung der Beute 

 zum Verwechseln ahnlich. Die direkte Beriihrung der Beute scheint 

 vermieden zu werden, um sie nicht wegzuschrecken, wenn sie dann 

 allwarts umstellt ist, vermag sie nicht mehr den verdauenden Einwir- 

 kungen ihres Kerkers zu entrinnen (p. 194). 



In 1904 Jennings published an extensive paper on the general 

 behavior of ameba, in which he showed that differences in surface 

 tension and the action of other mechanical principles do not ex- 

 plain satisfactorily some of the more important features of 

 ameban behavior. Several interesting observations on feeding 

 are also recorded. Some of these will be discussed further on 

 (pp. 563, 566). 



Kepner, Taliaferro et al. ('13) recorded some interesting varia- 

 tions of food cup formation in amebas. These observers con- 

 cluded that amebas react by the method of trial and error and 

 that "in each reaction there is evidence of purposiveness" (p. 

 421) . This point will be discussed in a later paper. 



Character and formation of food cups 



The larger amount of feeding in the granular amebas, and 

 practically all the feeding of the raptorial, is accomplished by 

 enveloping the food object in a cup of protoplasm which does not 

 come into contact with the food object until the cup is practi- 

 cally completed. Such a cup is not formed except over food, or 

 in the vicinity of objects which possess qualities that have be- 

 come associated by the ameba with food. The temi 'food cup' 

 is therefore employed to designate this extemporized structure 

 by means of which the ameba eats solid substances. 



As observed under the microscope, a food cup is formed in sev- 

 eral ways, depending upon the character, size, and movement of 



