OBSERVATIONS ON FEEDING OF AMEBA 37 



ber 20, 12 m. a specimen containing a large rotifer, already par- 

 tially digested, was isolated. Three days later the rotifer, al- 

 though somewhat smaller, was still intact and apparently far 

 from completely digested (fig. 2) . During all this time the ameba 

 was kept at room temperature, about 22°, and it was active and 

 in excellent condition. Another specimen containing a rotifer 

 was isolated December 3. Two days later this specimen had 

 divided, but one of the daughters still retained the vacuole con- 

 taining the rotifer. Similar results were obtained in a number 

 of other cases. Greenwood ('87, p. 284) maintains that rotifers 

 are retained one to three days. 



Feeding on nematodes. Small nematodes were found in our 

 cultures at different times but they were never very abundant. 

 These creatures are extremely active. They almost incessantly 

 wriggle about so violently that it seems impossible for an ameba 

 to capture them. 



The process of feeding on these creatures was observed in only 

 one case and in this the nematode was more than half swallowed 

 when it was discovered (fig. 3) . The anterior end protruded and 

 this was waving about in the most violent fashion. The process 

 of swallowing continued, however, and fifteen minutes later the 

 worm was entirely engulfed. The ameba then became very 

 active, although there was no locomotion; it merely alternately 

 elongated and contracted, extending in nearly opposite direc- 

 tions each succeeding time; and each time it stretched out, the 

 nematode which constantly remained at the posterior end, was 

 folded more closely on itself and forced into a smaller space. 

 Thus the ameba continued to elongate first in one direction then 

 in another until the worm was well coiled up so as to form a 

 rather concentrated vacuole after which it slowly moved away 

 (fig. 3). The ameba was isolated shortly after this time. Two 

 days later it had divided and the vacuole had disappeared. It 

 would consequently appear to require less time to digest these 

 animals than it requires to digest rotifers. 



Feeding on ciliates. The following observations were made 

 by Mr. F. M. Root and the description is essentially as presented 

 by him. 



