REACTION TO LIGHT AND OTHER POINTS IN THE BEHAVIOR 



OF THE STARFISH. 



BY R. P. COWLES. 



The experiments described below deal largely with the reactions of 

 starfishes to light. Two species are used, namely: Astropecten duplicatus 

 and Echinaster crassispina, both of which occur near the Tortugas 

 group off Key West, Florida. 



Echinaster crassispina is rather common in the latter part of June 

 (1900) on the sandy and flat rocky bottom at the south side of Boca 

 Grande, one of the keys lying between Key West and Tortugas. In this 

 region the bottom is fairly level and much of it is of white sand; in some 

 places, however, flat stretches of rock extend horizontally above the 

 level of the sand and these are often covered with algag, corallines, gor- 

 gonia, etc. The echinasters usually live in about 2 feet of water at low 

 tide and they seem to be distributed irrespective of the character of the 

 bottom, about as many being found on the white sand as on the rocky 

 places. They are decidedly migratory and use their tube feet in moving 

 about over the sand in much the same manner as human beings use 

 their legs. This characteristic was observed by Romanes and Ewart 

 (1881) and by Preyer (1886-1887). Recently Jennings (1907), in his 

 usual clear manner, has studied and described the behavior of the tube 

 feet of Asterias forreri de Loriol, confirming the observations of the 

 earlier workers. Unlike A. forreri, the suckers of E. crassispina and A. 

 duplicatus do not adhere tightly to the substratum as a rule, nor do these 

 two species usually occur on the under side of rocks. 



The rather level character of the bottom on which Echinaster lives 

 leads one to believe that the animal is seldom turned over and therefore 

 seldom finds it necessary to right itself. I can hardly believe that this 

 turning over occurs so often that an echinaster would have a chance to 

 form a habit of righting itself on any one pair of rays, but there might be 

 some structural peculiarity which would determine the pair to be used. 



Echinaster lives in the open and seems always to be found in regions 

 exposed to the brightest light. In this respect it differs from A. forreri. 

 So, as would naturally be expected, we find that in experiments in the 

 laboratory Echinaster .crassispina reacts positively to bright light and 

 Asterias forreri reacts negatively. 



Astropecten duplicatus has somewhat similar habits to those of 

 Echinaster. It lives usually in deeper water, being found at a depth of 

 i or 2 fathoms. It is migratory, but suckers on the tube feet seem to 

 be practically absent. This form also lives on the sandy bottom and 

 reacts positively to bright light. 



NOTE. I wish to express my thanks to the Carnegie Institution and to Dr. 

 Alfred G. Mayer for the privilege of working in the Tortugas Laboratory. 



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