2o6 0. C. Glaser » 



Unpaar voran, in which according to von Uexkiill effective move- 

 ments occur in the two arms which are usually dragged passively 

 behind, I have observed that Ophiurabrevispina moves in practic- 

 ally all the ways in which it is possible for a pentaradiate animal of 

 its construction to move. 



INDIVIDUALITY 



The movements described are directly dependent upon the 

 pentaradiate symmetry, but this symmetry does not exhaust the 

 possibilities of behavior. A little observation shows that each 

 animal is unique at any given time and that while its movements 

 fall within the system of classification proposed, they have pecu- 

 liarities that distinguish them from other movements of the same 

 type. 



In general the movements may be either rapid or slow, and 

 certain individuals seem on first acquaintance to be distinctly 

 active or distinctly sluggish. More careful study shows, however, 

 that very sudden changes of behavior occur, and that an active, 

 rapidly moving animal may unexpectedly enter into a state of 

 sluggishness that sometimes lasts for hours. I do not understand 

 these sudden changes. They are not due to the conditions in the 

 aquaria; they occur with great suddenness and not in all of the 

 animals; they are not due to either gentleness or roughness in 

 handling because either may or may not be followed by a change 

 in the behavior of the same individual in successive trials. Possi- 

 bly any sort of handling may, in certain physiological states, cause 

 a change of behavior, but what the physiological state in which this 

 occurs is, is hard to ascertain. In certain experiments in which I 

 encumbered the arms with rubber tubes, after the manner of 

 Preyer ('86), I frequently encountered the same sudden change 

 from activity to passivity, and arms which were flexible and easily 

 encumbered, would suddenly bend at their tips and stiffen, so that 

 it was impossible to slip the tube over them. This stiffening might 

 take place at the first trial, or some other one, and never again, or it 

 might reoccur upon every attempt to encumber the arm. 



Periodic changes from activity to sluggishness also occur. 



