-23- 



and the glass It also involved the trenching loose of a number of 

 refraotory tube feet. 



On sand it was found that the animal could pull 15 gm 



W'ltll 



( without load) and tfce a load of 80 gm 



oould pull about '62 gm* 



OUORPINAVK.^f OF TH;; TUB& g&ffi 



Preliminary description. 



When starfish were suspended and the tube feet at the end 

 of one of the rays brought in oontiot with some solid object, those 

 that touched it first ~?are usually observed to attach* Then the 

 neighboring tube feat orient -3d and extended themselves in the same 

 direction 13 the attached tube feet* If opportunity offered theae 

 other tube feot attached as did the first tube feet* 



If no'* these tube feet are stimulatad sharply they retract 

 and the neighboring tube feet also retract (Roman* and >iwert 1881, 

 Prayer 1836, etc*,}* The wave of retraction passes down the stimula- 

 ted arm, and out the other arms along the line of the ambulacra! 

 nervous system. This is in accordance with the older observers, es- 

 pecially Preyer (1386)* They also stowed that if the nervous syatea 

 was cut <*t some point the above coordination would extend as far a 



the cut and no farther* 



r 

 Further than the fact that it rests in the ambulaoial 



nervous system, the mechanism of this coordination is very obscure* 

 Physiologically, it is a fact attested so far as I am aware by all 

 of the workers on this phase of echinodezm physiology* one tube 

 foot seems to "imitate" in its activity th behavior of its neigh- 

 bora* In the following analysis of coordination in the tube feet 

 we shall inquire into its 



