704 GEOFFREY LAPAGE 



actually disagreeable to the endoplasm, though not to the 

 ectoplasm, and not merely because it was indigestible. Further, 

 a piece of carmine was eaten only once if the amoeba was only 

 mildly hungry ; several times if it was very hungry ; but the 

 amoebae showed less and less inclination to ingest the same 

 grain if it were offered to them several times in succession. 

 The same was true if a number of different grains were offered, 

 each only once. 



It is obvious, therefore, that the factors which govern the 

 feeding of amoebae are by no means simple. It is probably for 

 this reason that I have been unable to induce my amoebae to 

 repeat their performance of 1920, either in the old or in fresh 

 cultures, on anything like the same scale. I have also looked 

 carefully for similar phenomena in thick cultures of Amoeba 

 proteus obtained by the methods of Taylor (27) and Doflein 

 {%). But, although these amoebae often exist in such numbers 

 that they are in close contact, and are actively feeding upon 

 Colpidium and Chilomonas, i. e. upon a carnivorous diet, they 

 have never showed the slightest tendency to ingest one another. 

 Schaeffer (23) also found that his amoebae, although they 

 were eating Ciliates and Flagellates readily, never ingested 

 one another. Further, Doflein (9), in his study of Amoeba 

 vespertilio, does not mention any case of their ingesting 

 one another. He used, however, chiefly amoebae containing 

 zoochlorellae, whose metabolism must have been, therefore, 

 abundantly provided for even in the absence of their normal 

 diet ; and in my own cultures of Amoebae vespertilio 

 containing zoochlorellae, relatively very few of the amoebae 

 contained spheres, and in those which did the spheres also 

 contained zoochlorellae. 



It is very likely, therefore, that the epidemic of cannibalism 

 which is described in this paper was an isolated occurrence, 

 dependent for its causation upon the physical and chemical 

 constitution of the culture medium and also, as Schaeffer's 

 work shows, upon the physiological condition of the amoebae 

 themselves. The fact that, in those other cases in which 

 similar phenomena have been observed in other than isolated 



