-15* 



(1) What is the stimulus which sets if off? (2) what factors 

 govern its orientation? (3) What is the Status of the 

 attaching reflex in the various stages of its accomplishment. 

 (4) What is the relative strength of the otep reflex in 

 different species* 



The stimulus 



The stimulus which sets off the step reflex is one of 

 gentle contact on the disc, contact on the column or harsh 

 stimulation of the disc results in a simple withdrawal. In 

 absence of contact stimulation, there is no approach toward 

 the ste/p reflex. I have seen a large ffyonopodia on its back 

 in shallow water, remain with a large part of its 22,000 

 (Verrill 1914) tube feet extended in one direction (the direc- 

 tion changing from time to tine) for half an hour, with 



' wjP * ^^r i*f 



none of the tube feet executing the step reflex* When, however 

 a light object, tmch a piece of celluloid was plaoed on the 

 tube feet the step reflex immediately started in all of the 

 tube feet receiving the contact stimulation* As a result the 

 piece of celluloid was quickly "walked* to the temporary 

 posterior of the starfish* The same was repeated with a very 

 thin clear glass watch-crystal* The glass could not be seen 

 at all, under water, but its course across the tube feet could 

 be clearly followed by observing the area in which the pedicels 

 were executing the step-reflex* 



Ihen a starfish in aotive locomotion is brought above 

 the surface of the water the step reflex was seen to occur 

 without further stimulus* An aotive specimen of Pyonopodia 

 with the ventral side exposed to the air, presents 

 the likeness of some strange sort of military activity. lth 

 m*chinf like regularity the 22,000 bright yellow tube feet 



