24* 



characteristics la the rigid starfish, and compare it vith 

 the ooordination manifested by the gills* '** wtti ilso inquire 

 into coordination in tube feet of active but non-oriented starfish, 

 the building up of this ooordination into the Unified impulse, 

 the behavior of tha starfish under the influence of the unified 

 impulse and the breaking do-am of this unified impulse under 

 various normal and abnormal conditions, 



Coordination i& the tube*feet g the rigid '.atjarfish, 

 When rigid speoimene of Pisaster were suspended or inverted 

 the tube feet, after their temporary retraction from the stimula* 

 tion of loosening, were found to extend more or less at right 

 angles to the body of the ray. There were subsequent movements 

 of the ray *hioh vill be considered later* Some of the tube feet 

 were then stimulated to retract* There was a wave of retraction 

 passing along the lines of the tube feet* This lessened in 



& d'ld 



intensity as it proceeded from its source, so that it *y no 

 reach the farthest tube feet. Later the tube feet WM again extend 

 the wave of extension pawling back in the reverse order so that 

 the tube feet stimulated to retraot and those nearest them will 

 be the last to re extend* 



To account for this ooordination in retraction and extension 

 it is not necessary to hypothesise very complex conditions in the 

 nervous system at the base of the pedicels* 



^'.uenftt (1888) Ludwig and Hainan (1899) ; tfeyer (1916) eto.,X the 

 ambulaoral nervous system seems to be merely a condensation 

 of the nerve net that extends over the outside of the myoderral 

 heath* So far aa I am aware there is no morphological evidence 

 of synapses in the nervous system of starfiahos, though of course 

 the evidence on this question is far from complete* A simple, 

 nerve net will account for the above behavior* 



