13ft- 

 Description of the step reflex. 



Under ordinary cireunstanoes of locomotion, this lateral 

 oreaeat is followed by retraction and toe retraction by re*extenaion 

 in the direction of locomotion. This infolres contact vith the sub- 

 strata and UM itiaulations -*hich gire rise to the repetition of the 

 lashing baek, the retraction and the re*ztension These aoTeaents 

 vhioh inrolre, as sho-vn in detail later, attaohnent to tha substrate, 

 are tl'x>se of ordinary locomotion, iadi tube foot, acting indepeadeat- 

 ly as to tiae but in hansony with its felloes as to direction, re* 

 peats these ao Yemenis as long as contact stiaculi result H usi extension 

 and the locoaotor iapulse reaain unimpaired* 



