Selection of Food in Stentor Cceriilens (Ehr.) 



89 



the coarser particles had settled down the finer particles were 

 siphoned off to be used in the experiment. The water in which 

 the sulphur was stirred up was filtered water from the Stentor cul- 

 ture, so that the results of the experiment cannot be attributed to 

 any pecuhar qualities of the water. Some of the particles of sul- 

 phur were sucked up into a pipette together with some living 

 Phacus triqueter, as previously described. This mixture of Pha- 

 cus and sulphur was then fed on to the disk of a normally behav- 

 ing Stentor in the fully extended condition, and the path and fate 

 of each particle recorded. The results follow: 



The particles are numbered in the order in which they reached the disk of the Stentor. The sulphur 

 particles are denominated "s,'' the Phacus "p.'' Thus, 7s in the "rejected'' column signifies that 

 the seventh particle was sulphur, and that it was rejected. Where several numbers are bracketed, 

 it signifies that these particles were fed simultaneously. In the column headed "loops'' is shown the 

 number of loops made by the particle. (See p. 11). The column headed "size'' gives the size of 

 the sulphur particles in units of the size of Phacus. Thus I, means same size as Phacus, .5 means 

 one-half that size. 



TABLE I 



SUMMARY 



Eaten, 12 Phacus and i grain of sulphur. 

 Rejected, 3 Phacus and 13 grains of sulphur. 



