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



bearing the food bends downward, applying it to a new region, 

 while the point first bent straightens out. Thus the food is passed 

 from one set of tube feet to another, slowly along the under side 

 of the ray till it reaches the mouth. 



When the stomach is passed out of the mouth in feeding, it 

 usually appears as five yellowish lobes or sacs. These fold about 

 the prey, partly envelope it, and insert themselves into its cavi- 

 ties and angles. But the prey is never, so far as I have observed, 

 actually within a sac formed by the stomach ; it merely has these 

 lobes closely applied to it. The lobes seek out especially the soft 

 parts of the food, leaving hard parts as a rule quite uncovered. 

 The stomach lobes are transparent and contain a clear yellowish 

 fluid. Sometimes Asterias everts the stomach and applies its 

 lobes to the surface of the glass bottom of the aquarium, appar- 

 ently absorbing the mucus and other organic material which has 

 formed a layer over the surface. In one case the lobes extended 

 thus two or three centimeters from the mouth, reaching more 

 than a centimeter beyond the edge of the disk, so as to be seen 

 from above. The lobes moved about freely, exploring the sur- 

 face. They were withdrawn as soon as the starfish was disturbed. 



Behavior of the Starfish in Selecting the Conditions of 



Existence. 



"We have thus far seen how the starfish gets the material for 

 carrying on its chemical processes, — food and oxygen, — and how 

 it protects the delicate organs that are engaged in getting oxygen, 

 by the action of the pedicellariae. But there are other require- 

 ments for existence. The starfish must live under proper ex- 

 ternal conditions if the life processes are to continue. It must 

 not be crushed; it must not be poisoned; it must not be too hot 

 or too cold. Many of the common agents of nature tend to injure 

 or destroy it. How far does the starfish succeed in keeping itself 

 under conditions that are favorable to its life processes, and how 

 does it do this? 



Undoubtedly the fact that the adult starfish is found in condi- 

 tions which favor its life processes is partly due to the fact that 

 nil those which were not under such conditions have died. The 



