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Fig. 1 Camera sketches of a rotifer and an ameba which has been feeding on 

 rotifiers: n, nucleus; c, contractile vacuole;/, food vacuole, containing rotifiers; 

 e, eyes; p, pharynx; mm, projected scale. 



A Ameba and rotifier showing their relative size under normal conditions. 

 Drawn November 20,. 12 m. Note the large food vacuole in the ameba. It con- 

 tains one large and two small rotifers, all partially digested and apparently much 

 decreased in size. Only one of the small rotifers is shown in the sketch. Both 

 were attached to the large one when it was captured and they were swallowed 

 with it. 



B The same ameba showing the three rotifers in the food vacuoles. Drawn 

 November 20, 12.40 p.m. 



C and D Same ameba drawn November '3, 11 and 11.05 a.m., respectively. 

 Note that the rotifers in the food vacuoles have apparently become somewhat 

 smaller during the preceding three days. They also became more translucent, 

 but they were apparently still far from being completely digested. Moreover, 

 when the ameba was discovered they were already much smaller than normal, 

 indicating that they had been captured a considerable time earlier (compare 

 with fig. 2e). Thus it is evident that in this case it would have required much more 

 than three days to digest the rotifers. When the last sketch was made the ameba 

 was active and apparently in excellent condition, but three hours later it was 

 found dead and partially disintegrated. 



34 



