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



5. Effects of Physiological Condition; Reaction to the Situa- 

 tion as a Whole. — As a result of the factors set forth in para- 

 graphs 1-1, as well as of others of similar character, the behavior 

 of the starfish when subjected to a given stimulus is extremely 

 variable. It depends on the simultaneous presence of other 

 stimuli, on past stimuli that have acted on the animal, on its 

 past reactions, on the way it is behaving at the time the stimulus 

 acts upon it, and on various other factors. These can nearly all 

 be sunnned up in the statement that the behavior of the starfish 

 under given external conditions depends on its physiological 

 state, and that its physiological states are varied and depend on 

 many factors. 



To put the matter in another way, how the starfish shall react 

 under given stimulation depends on circumstances, and on its 

 past experiences. Thus the starfish while walking in a certain 

 direction, like other animals, frequently avoids obstacles against 

 which it comes; it reacts, as we say, negatively to mechanical 

 stimuli. But when it has been placed in new surroundings, as in 

 a jar or aquarium, and is moving about on a tour of exploration, 

 it; reacts for a time in the opposite manner. When a ray comes 

 in contact with an object, the starfish turns and creeps toward 

 that, until it has explored it well. Then, if the object presents 

 no opportunities for a protective retreat, the starfish leaves it 

 and moves on. 



One of the things which the starfish avoids most consistently, 

 under ordinary conditions, is leaving the water. When it comes 

 to the edge of a pool or aquarium where the tip of a ray projects 

 out of the water, the animal withdraws. There is of course, from 

 the standpoint of regulation, good reason for this, since drying 

 up is destructive. Furthermore, as Ave have seen, the starfish 

 usually shows a decided avoidance of light, retreating from the 

 lighted side of a vessel. But under certain conditions both its 

 repugnance to exposure to air and to light are overcome for a 

 time. This occurs when the starfish has been transferred to a 

 new region, and is exploring it. It proceeds to explore light as 

 well as dark regions, and even ventures to reach far out into the 

 air. Description of a typical example will bring out the essential 

 points in such behavior. 



