684 geoffrey lapage 



6. Ingestion of the Sphere. 



The extrusion of the spheres and the development of some 

 of them into small amoebae had been seen before I was fortunate 

 enough to observe an amoeba actually ingesting a free sphere. 

 I had just watched the extrusion of this sphere, and the amoeba 

 which had extruded it had hardly moved out of the field before 

 another amoeba entered and immediately took up the sphere 

 which the other had left behind. Further observation showed 

 that this fate was suffered not only by the motionless spheres 

 but also by those which had already become transformed into 

 small active amoebae. 



The process of ingestion was perfectly normal in every way. 

 The big amoebae put out pseudopodia round the sphere and 

 gradually enclosed it in a typical food vacuole. The result was 

 an amoeba containing a sphere, exactly resembling the original 

 amoeba, with a sphere inside it, which had awakened my 

 interest at the beginning of the observations. 



Not long afterwards I was able to follow and to sketch, the 

 dramatic chase of a small Amoeba limax by a large active 

 Amoeba vespertilio. Text-fig. c gives the details of this 

 drama. It will be seen that the large amoeba at first attempted 

 to surround its prey (4, 5, and 6), and, after cutting off its 

 retreat, nearly succeeded in enclosing it (7 and 8). At 9 the 

 small amoeba is not inside the large one, but underneath it, the 

 Amoeba vespertilio having streamed over the Amoeba 

 limax so as to hold it between itself and the glass. I have 

 often seen Amoeba pro tens capture Paramoecium and 

 other Ciliates in the same manner. The Amoeba limax, 

 however, was too nimble in this instance, for it escaped again 

 (10) and the large amoeba made no further attempt to capture 

 it. A similar case has been described and figured by Jennings 

 (16), in which the amoeba also failed to secure its prey. Jen- 

 nings concluded that the behaviour of the captor to the victim 

 could not be explained as the result of chemical or tactile 

 stimuli only, but that there was a finely co-ordinated adapta- 

 tion of the movements of the captor to those of the victim, 



