-52- 



ooaiplioited coordination cf movements thit are involved in the 

 deviation reaction* 



iMMl f ^ tn *^' y< * aspects pf the "deviation push" oji different 

 substrates and witft different feints on the animal vary *ith 

 mechanical conditions while quantitative aspects olT oontaot 

 stimuli required to initiate the negative reaction dft not. 



It was thought that the auount of push which the deviating 

 animal exerted upon the obstacle -whenjoonsidered in oonneotion 

 with itB pulling Ability, and other reactions might thro light 

 upon the mechanisms of the deviation reaction. The amount 

 of push was measured by attaching the obstacle, a lever, swinging 

 freely frofr a rigid fulcrum by a thread to the recording 

 spring above described* The push, then was recorded as the 

 height of the curve, written on the slowly revolving drum* The 

 appearance of the curve was as below for the different species 

 studied* 



The push continues to increase until t&a deviation begins, that 

 is, until the effectors (tube feet or spines) on one side of the 

 body begin to reverse themselves and the rotation around the 

 obstacle as an axis is initiated* From then on there is an 

 irregular decline in the push until the naoDdb animal is free 

 of the obstacle* ith the drum running at the same speed, the 

 shape of the curve as well ae its height is dependent upon the 

 aotivity of the specimen studied* This was taken into account 

 so as to get results as comparable as possible* If The sea urchin 



1 1 roa/ry l o c en trp t ep franoisoanua was found to be mowing on sand 

 by means of its spines only. In deviating around an obstacle 



