132 University of California Publications in Zoology. [Vol. 4 



1. Some starfish when placed on their backs (dorsal surface 

 down, ventral surface up) at once lift up all their rays, — bend- 

 ing? them toward the ventral side. The rays now wave about 

 back and forth in the water, as if feeling for something-. Then 

 one or two begin to bend downward (dorsally), while at the 

 same time they may begin to twist at the tip, so as to bring the 

 ventral side below. Reaching the bottom, they attach and turn 

 the starfish. 



2. In other cases the first tendency seen is to bend all the 

 arms downward (dorsally) instead of upward. Thus all quickly 

 come in contact with the bottom ; some or all twist and attach ; 

 some of the rays may rise and swing over and the starfish is 

 turned. 



3. Often at first some of the rays are lifted up (ventrally) 

 and feel about, while others are bent down (dorsally), and 

 twisted. The rays thus behaving differently may be variously 

 distributed ; the same ray may first bend downward, then before 

 reaching bottom bend upward, or vice versa. The same ray may 

 change its role several times before the method of turning is 

 settled. 



In all of the three types thus far mentioned, the rays which 

 bend downward and attach may twist in various ways, so that 

 they may not assist each other, or may even pull in opposite 

 directions. Then there is likely to be some ineffectual pulling 

 and hauling till certain rays untwist and change their method 

 of action, and the righting finally occurs in a unified way. 



4. Often when a starfish is turned on its back, there is evi- 

 dent an immediate set toward turning in a certain unified way, — 

 a coordinated general impulse, appearing at once. Two of the 

 rays, for example, will at once begin to bend downward (dor- 

 sally) and to twist in such a way as to take hold in a coordinate 

 manner. At the same time the other three rays begin to rise up 

 and go over, their tube feet all being directed from the begin- 

 ning to the side toward which the turning is to occur; they are 

 prepared as it were for meeting the bottom as soon as the turning 

 is completed. 



The Eighting Impulse. — This unified, coordinated impulse 

 toward turning in a definite way is perhaps the most striking and 



