BEHAVIOR OF SEA-ANEMONES. 2J J 



chamber and thus exposing the specimens to the light, within 

 two minutes, indeed, almost immediately, they began to retract. 

 This reaction is not sudden or general at once, as in such creatures 

 as the earthworm, but begins in a somewhat indefinite movement 

 of the body, accompanied by similar movements of the tentacles, 

 followed very soon by a slow but definite retraction of the entire 

 body within the tube, often including likewise the tentacles as 

 well. 



The experiment was later repeated in a room where it was 

 possible to utilize direct sunlight. Under these conditions the 

 reaction was much more energetic and definite, as might be ex- 

 pected. Variously modified, the experiments were performed 

 repeatedly, perhaps fifty times, and with substantially the same 

 results, though, as will be noted in a later connection, exhibiting 

 variations of response. In some cases the reaction was so defi- 

 nite and prompt as to leave the impression on the observer that 

 the creature was possessed of something akin to visual sensation. 

 At other times the reactions were indefinite, sluggish, variable, 

 and less convincing, though in the end resulting in the retraction 

 of the specimen as before. 



The following experiment was made to determine the extent 

 of the sensory area, or in other words whether all portions of 

 the body were similarly responsive to light. A specimen which 

 had been quietly expanded on the surface of the sand for some 

 time, being one of those which had shown less aptitude for bur- 

 rowing, was so placed as to make it possible to reflect a harrow 

 ray of light upon sharply defined parts of the body or tentacles. 

 It was found that the oral region, including about one third of 

 the body, was distinctly more sensitive than was any other. 

 Light concentrated on the aboral portion seemed to have no 

 effect at all, or so slight as to be indistinguishable. The tentacles 

 were apparently less responsive than the immediately adjacent 

 oral part of the body. This is slightly different from the con- 

 dition found in Sagartia modesta, as will be noted later, and was 

 a matter of some surprise, since the pigmentation of the tips of 

 these organs might be thought to have some relation to sensory 

 functions. 



In a general way these results confirm the histological studies 



