CHOICE OF FOOD IN AMEBA 231 



little to do with it, for food particles like globulin are frequently 

 thrown out at once, while glass is always thrown out ; and choles- 

 terin, presumably an indigestible substance, was in one case 

 retained for over and hour and a half. The condition of hunger 

 in the ameba is one of the most important factors. But what- 

 ever the factors are which control retention, it is certain that 

 they are not the same as those conditioning ingestion. 



DISCUSSION OF EXPERIMENTAL RESULTS 



Choice of food. — What is choice? This is a very troublesome 

 concept in science. We need some such word as choice in 

 describing the reactions of animals in order to avoid hopelessly 

 confusing circumlocutions, and yet it seems impossible to give 

 a satisfactory definition of choice from an objective point of 

 view. Since I wish to discuss particularly the phenomena of 

 choice of food in this paper, I shall undertake to explain how 

 I use this word. 



Choice has been used to label a process by which a certain 

 state of matter in a system is brought about. More restrictively, 

 it has been used to designate exclusively the end result of such 

 a process, the state of matter after the process has ceased. It 

 is obvious, without illustration, that these two meanings of the 

 word are quite distinct from each other and that they can con- 

 veniently be qualified by using, respectively, the phrases " pro- 

 cess of " and " result of " choice. The word choice is also some- 

 times used to describe such processes as, for example, the action 

 of a magnet upon a mixture of sand and iron filings. This is an 

 unfortunate use of the word and two objections may be urged 

 against this usage: first, an equally intelligible description of the 

 action of the magnet can be given without the use of the word 

 choice; second, choice might with equal propriety, be applied to 

 every movement of matter in the universe. It is therefore a 

 hindrance to clear thinking to use the word choice as descrip- 

 tive or nominative of such processes as these. 



Again, the concept of choice is frequently restricted to pro- 

 cesses observed in organisms, that is, to conscious processes. 

 This view, although of the greatest interest, is very difficult to 

 consider from our present objective experimental point of view, 

 since it would be necessary first to determine whether an animal 

 whose power of choice is in question, possesses consciousness. 



