-61- 



Deaoription of various other oorrelatgd movements o_f the 

 tube feet and 2JS&* 



If an aotive Pisaster be suspended in -water and away from 

 contact stimulation, the rays move about for a while, flexing them- 

 selves doraally and laterally, in m manner that we shall discuss 

 latar, but eventually assume a state of vantro -flexion similar to 

 that assumed by the rigid animal* The aotive animal in vsntro flex* 

 ion differs, however, from the rigid or the niootinized animal in 

 that contact stimulations at onoe set up activities of the tube feat 

 and arms* The tube feat raaot positively to gentle contact stimula- 

 tion and retraot upon sever* stimulation. We have followed the im- 

 mediate responses of the anas to these stimulations, but the positive 

 and negative activities of the tube fset spread to the tube feet of 

 the rest of the animal, as also do the corresponding movements of 

 the arms* 'ihus if the stimulation be quite harsh the tube feet will 

 retraot over the wnola animal and the arms themselves will become 

 shorter and more rigid* 



In oonneotion with the positive response of the tube feet, 

 ir will be remembered that this does not spread as well when the tube 

 feet are free from contaot as it dies when they are executing the 

 step reflex* A weak positive response theo, such as the positive dif- 

 ferential activity of the unstimulated anas in case of a harshly tim- 

 ulatad animal, hardly makes itself notiovable in the suspended animal 

 as it does in the ae&ativt response of the animal locomoting on a sub- 

 strata* 



Ascription oj; th..a formation the coordinated jlmpulse T yhen 

 the tuba feet are free o the substrata* 



A strong positive response, on the other hand, does spread, 

 and in spreading involves movements of the arm, as the following ex- 

 periment will show. An aotive Pieaster suspended and in a state of 



