RELATIONS OF BURSARIA TO FOOD 



9 



formation of the vacuole. This is always definite and can 

 generally be readily observed and followed throughout the 

 process. This is exemplified by the following experiment: 



Experiment II. Single normal individuals which had been placed 

 in tap water 24 hours previously, were each fed a single grain of fresh 

 yolk and the time interval noted between the separation of the vacuole 

 from the base of the gullet and the point of complete disappearance of 

 the liquid about the yolk grain. 



Table 1 shows records from ten individuals each fed one grain. 

 From the table it will be seen that the duration of the process is 

 relatively uniform. The point when all the liquid about the 

 grain has been absorbed was determined to within about thirty 

 seconds. 



TABLE 1 

 Experiment II 



WTien more than one grain is enclosed in the vacuole the same 

 process of absorption takes place, following the separation of the 

 vacuole from the base of the gullet; the vacuole membrane be- 

 coming closely applied to the surface of the grains as is shown in 

 figure 2. 



Different vacuoles in the same cell are quite independent as 

 to the absorption of fluid. To illustrate, figure 3 is given. Here 

 the new vacuole contained a comparatively large amount of liquid 

 about the grain (in most cases the quantity of hquid is less), 

 and came to be located close to an older vacuole in which the 

 process of digestion of a Paramecium had. practically been com- 

 pleted, and which contained a considerable quantity of liquid. 

 The vacuole containing the digested Paramecium was unaffected 

 in size by the absorption of the Uquid about the yolk grain in 

 the newly formed vacuole. 



An explanation on the basis of osmotic relations within the 

 cytoplasm and in the vacuoles, assuming the vacuole membrane 



