Il8 Asa Arthur Schaejjer 



7 Few Euglen^. Result: Comparatively few Euglenae eaten. 



Some peculiarities ot behavior of the Stentors in the above 

 series of experiments may be worth mentioning. About 60 per 

 cent of the Stentors were swimming freely. In dishes 4 and 6 

 where the Chilomonas were dense, the Stentors swam continuously 

 with the foot ahead. About one-third of all the free-swimming 

 Stentors in dishes 2 and 4 (where the Chilomonas were dense) 

 were in a state of almost maximum contraction. These Stentors 

 conta ned very few Chilomonas. Nearly all the free-swimming 

 Stentors in the other dishes were extended. Some of the attached 

 Stentors in the dishes 2 and 4 were maximally contracted. These 

 contained the smallest number of food organisms. Some of the 

 other attached Stentors rolled masses of Chilomonas on the disk 

 in the "push ball" fashion as described on page 86. The other 

 attached Stentors in these dishes continually reversed their cilia. 

 The attached Stentors in the Euglena dishes, i, 3, 6 and 7, kept 

 all the body cilia beating forward, whether all the Euglena were 

 rejected or all eaten. 



We have seen that Stentor takes less waste matter (carmine, 

 etc.) when food is present, more when it is absent. This brmgs 

 up another interesting question. In order that the animal shall 

 reject substances not good for food, must it first have taken a 

 certain amount of food? If so, how much food must be taken 

 before discrimination begins? And in order to induce discrimina- 

 tion, is it necessary that food should be actually ingested, or is 

 mere contact with food all that is required? 



As to the quantity of food necessary to induce discrimination 

 the experiments just described show that Stentor discriminates 

 against carmine (or Chilomonas), about as completely when the 

 proportion of Euglenae present is very small (about i : 100) as 

 when more Euglenae are present. It is impracticable to work with 

 smaller proportions of Euglenae, since in such cases one cannot 

 keep the various kinds of particles uniformly distributed. 



To determine whether actual ingestion of food, or only contact 

 with it, is necessary to induce discrimination, the following experi- 

 ment was tried. The waste material, carmine, was mixed with 

 rather large paramecia. The latter mav serve as food for Stentor, 



