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scattered individuals may be found on muddy or sandy shores, but 

 they are quite scarce. They are often found clinging to pilings, 

 old boats, and other objects in the water. By action of the tube 

 feet they are able to cling very tenaciously to almost any solid 

 object. At low tide they may be found under the rocks, out of the 

 sun, where they are protected from the heat and drying. Due to 

 a food relationship they are usually found in the same area with 

 marine clams, oysters, and rock barnacles. During the day they 



Fig. 135. — The ochre starfish, Pisaster ochraceus, an abundant form along the 

 Pacific coast. (Johnson and Snook, Seashore Animals of the Pacific Coasts The 

 Macmillan Company.) 



are rather inactive, but at night they are much more active and 

 respond to such stimuli as light, temperature, contact, and chemicals. 

 It has been demonstrated experimentally that starfishes may form 

 habits. They ordinarily live and move about with the oral side 

 next to the substratum, and if turned over, will right themselves 

 in the same way time after time. If the arms which are habitually 

 used for this are incapacitated, they will acquire the habit of using 

 another combination of rays in this act. 



