Food Selection Among Lower Animals. 39 



The main object of the experimental work was to change the 

 taste of the organisms, or to change their form, surface texture, 

 etc., without, so far as possible, changing the taste, to see what 

 the effect would be on the stentor. A number of food organisms, 

 phacus, were cooked and washed. They were then fed with liv- 

 ing phacus in a mixed stream. The result was that the hungry 

 stentors ate all the phacus whether cooked or living; and those 

 that were partially satiated ate a few of both sorts and rejected 

 the greater number of both. Other phacus were treated with 

 iodine, quinine, acids, dyes, etc., then washed and fed with living 

 phacus in a mixed stream. But again there was no selection. 

 Cooking phacus and treating them with various chemicals should 

 change their taste; nevertheless whatever change was thus pro- 

 duced, was without effect in their discrimination of food. 



In other experiments the living food organisms were mashed 

 up into a jelly. The form of the organisms was thus completely 

 destroyed. This jelly was rejected. Not any of it was eaten. 

 But if the food organisms were cut up into quarters or eighths, 

 the pieces were eaten. In a few experiments starch grains were 

 soaked for a few minutes in the jelly of the organisms and then 

 fed to the stentor without washing. None of the starch grains 

 were eaten. Starch grains were also soaked in raw beef juice, 

 pork juice, pepsin, Liebig's Extract of Beef, sugar, etc., but in no 

 case was starch so treated eaten. 



Now taking all these experiments together, we see that when 

 the taste of the food objects was altered, no change in discrimina- 

 tion resulted ; but when the form and texture of the food sub- 

 stances were changed, marked effects on discrimination were ob- 

 served. This leads to the conclusion that the stentor selects its 

 food by a tactual sense; that the chemical sense, if the stentor pos- 

 sesses any, plays little part in the process. This conclusion need 

 not be surprising. For what sort of a taste may a living animal 

 have when it is swallowed whole with a quantity of water? It is 

 only the excretory products that diffuse out into the water from 

 a living animal.' The albumins and other proteins, carbohydrates 

 and fats do not diffuse out into the water, and these substances 

 are practically the only food substances in the animal. 



Some attempts were made to analyze the basis of selection still 

 further, but without much success. However, it is pretty certain 



