236 A. K. MOORE. 



sometimes for more than an hour, although further locomotion 

 was impossible, and no attempt at righting was made. In fact, 

 the starfish often retained such a slight attachment to the wall 

 of the aquarium that the surface film of the water could no 

 longer support the weight of the animal, with the consequence 

 that the latter fell to the bottom of the tank. In such cases the 

 tube feet cling to the surface film of the water because the film 

 acts as a solid surface; it cannot, however, bear the animal's 

 weight. Romanes 1 speaks of these movements as follows: "On 

 reaching the surface, the animal does not wish (!) to leave its 

 native element . . . and neither does it wish ( !) again to descend 

 into the levels from which it has just ascended. It therefore 

 begins to feel about for rocks or sea weeds at the surface, by 

 crawling along the side of the tank and every now and then 

 throwing back its uppermost ray or rays along the surface of 

 the water to feel for any solid support that may be within reach." 

 Romanes evidently was not familiar with surface tension. Had 

 he known that the surface film of a liquid acts like a solid surface 

 he would have been prevented from attributing intelligence to 

 the starfish. 



In order to see whether pressure on the gills might, as Jennings 

 states, cause the starfish to turn over, I supported a glass plate 

 in the aquarium, at a height just sufficient to press lightly on the 

 dorsal side of a starfish moving over the floor of the tank. This 

 was placed in the path of an approaching starfish. The latter 

 did not change its direction when the plate was touched, but 

 pursued its course, although the gills were pressed down. Fur- 

 thermore, if a starfish is allowed to attach itself to a glass plate 

 and is then suspended dorsal side downward so that it touches 

 the bottom, its movements continue normally, although it could 

 easily right itself if that were necessary. Clearly, then, pressure 

 on the gills is not one of the factors which causes a starfish to 

 right itself. 



The displacements of the internal organs which, we are assured, 

 "must occur" when the dorsal side is down, can only be due to 

 gravity. I have frequently observed large numbers of st.tNi^h 

 clinging, dorsal side downward, to overhanging ledges, feeding 



'Romanes, "Jellyfish. Starfish and Sea Urchins," p. 268. 



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