234 S. O. MAST 



larger lip. Lacrymaria on the other hand is not thus restricted 

 in the direction of turning; it can turn toward any side. This 

 does not mean that the direction in which this animal turns 

 is not definitely determined; it merely means that the deter- 

 mining factors are within the organism. There are also other 

 reactions in Lacrymaria which are clearly dependent upon 

 internal factors. As a matter of fact, without any immediate 

 environmental change whatever the oral cilia may become 

 quiet or active, or when striking backward they may all suddenly 

 reverse and strike forward causing the head to move backward, 

 or only those on one side may reverse, causing the head to move 

 side wise. Thus it is evident that it is possible to predict the 

 reaction of Lacrymaria only in a very general way. Its move- 

 ments are largely in accord with the generally accepted defi- 

 nition of random movements. It avoids objects and finds food 

 by trial, which means merely that the direction in ^^'hich the 

 animal moves is not definitely related to the location of external 

 objects, sources of stimuli, and that successive difterent axial 

 positions are taken until the animal succeeds in avoiding ob- 

 structions or in procuring food. 



We assume that all of these reactions are specifically associated 

 with physico-chemical phenomena in an orderly way, or to put it 

 in a more popular form, that they are mechanically regulated. 

 But for all that is known to the contrary, psychic phenomena 

 may be involved as is undoubtedly true with reference to certain 

 trial reactions in the human being, although the relation between 

 these reactions and the psychic phenomena is not well under- 

 stood. I shall refer to this question again under regulation of 

 the movements of the head. 



There is no indication of orientation in Lacrymaria, nothing in 

 the nature of a tropism as defined by Loeb (1906, p. 135, see 

 Mast, 191 1, pp. 54, 23-35), except perhaps in an electric current 

 in which the reactions have not been studied. 



FEEDING 



Lacrymaria ordinarily obtain their food by capturing and 

 swallowing small unicellular organisms. Occasionally, however, 

 specimens are found that obtain a certain amount of food from 

 a small globular plant which they contain, an alga. Some speci- 

 mens contain only a few of these minute plants while others are 



