126 University of Calif oritia I'ublications in Zoology. [Vol. 4 



Figures 12 and 13. — The earliest stages of the righting reaction of the 

 starfish. In Fig. 12 the two rays at the right have attached themselves in 

 a co-ordinated way, but the unified impulse has not yet appeared; the tube 

 feet of the different rays are extended in various directions. Figure 13 

 shows the conditions a little later; the co-ordinated impulse has appeared; 

 all the tube feet are directed to the right, and all the activities of the 

 starfish are henceforth devoted to turning in that direction. 



