212 



0. C. Glaser 



records when averaged show that these animals, on the whole, 

 may be expected to right themselves in less than 45 seconds. 

 One fact of considerable interest is clearly demonstrated by the 

 averages as well as by the individual records — there is no reduction 

 in the amount of time required to perform the righting act; in 

 other words, under normal conditions, these animals do not im- 

 prove by practice in the execution of their righting movements. 



PROBLEM SOLVING 



The expression "problem solving" is almost self-explanatory. 

 Under this heading, I have placed such behavior as an ophiuran 

 exhibited when stimulated by interference more or less unusual, 

 and from which it was able sooner or later to escape. What I did 

 was to observe the way in which the escape was made — the prob- 

 lem solved — and how much time was consumed in doing it. 



The problem — the same as that employed by Preyer— was to rid 

 one or more arms of the small pieces of loosely fitting rubber tub- 

 ing with which I enc umbered them. In the selection of individuals 

 for experiment, my choice was guided by two considerations: 



whether all the arms were approxi- 

 mately equal in length, neither 

 broken, nor recently regenerated; 

 and whether the individuals were 

 not too active to make the obser- 

 vations easy to record. 



When encumbered in the man- 

 ner represented in Fig. 5, an 

 ophiuran does many things, some 

 of which are recorded in von 

 Uexkiill's photographs. At first it 

 may pass through a brief latent 

 period, during which it lies motion- 

 less on the bottom of the dish, and 

 then it 'may crawl, dragging the 

 encumbered arm behind it. Often the animal moves at an angle 

 to the encumbered arm, or in rare cases in the direction of it. The 



Fig. 5 



