242 S. O. MAST 



SUMMARY 



1. Lacrymaria has the power of most remarkable extension 

 of the neck and freedom of movement of the head. The neck is 

 sometimes stretched out to a distance equal to eight times the 

 length of the body, about fifty times its own length, and while 

 thus extended the head in rapid succession turns and moves in 

 all directions exploring ever3^thing within this radius while the 

 body, usually concealed in debris, remains quiet. 



2. Detached heads perform all movements that attached ones 

 do except the backward movement. Practically all of the move- 

 ments except this one w^hich is caused by the contraction of 

 the neck, are due to the activity of the oral cilia. 



3. The direction in which the head turns is in all probability 

 regulated entirely by internal factors. It is independent of the 

 location of the stimulus, although the contraction of the neck 

 and the consequent backward movement of the head may 

 not be. 



4. The direction of locomotion of Lacrymaria in swimming is 

 regulated almost entirely by the movements of the head. The 

 head turns to the right and the left, upward and downward, 

 frequently suddenly and sharply; the body follows the head on 

 its tortuous course much as though they were organically inde- 

 pendent and united merely by a highly elastic fibre. 



5. Stimulation of the anterior end may not only cause con- 

 traction of the neck but also backward movement of the entire 

 organism, while stimulation of the posterior end usually causes 

 forward movement. This difference in reaction constitutes the 

 only evidence of the dependence of the behavior of Lacrymaria 

 upon the location of the stimulus. Practically all of the remain- 

 ing reactions are in the nature of random or trial movements, 

 movements which are determined largely by internal factors, the 

 nature of which is as yet unknown. 



6. There is no evidence of orientation in this organism and 

 nothing in the nature of a tropism as defined by Loeb with the 

 possible exception of its response to an electric current. 



7. The food of Lacrymaria, except in the few specimens which 

 contain symbiotic algae, probably consists entirely of unicellular 

 organisms w^hich are captured and swallowed alive. Some of 

 these organisms are half as large as the creatures which sw^allow 

 them. 



