2C>6 HARRY BEAL TORREY. 



action in response to the stimulus of gravity, so that as a result- 

 ant of the opposing responses, the polyp leaves the shell for the 

 glass as stated above. 



Light does not appear to stimulate 5. davisi in any way. The 

 polyps neither bend nor move toward the light when it comes 

 from but one side of the aquarium, in all degrees up to the in- 

 tensity of bright daylight. Neither do flashes of sunlight 

 falling upon polyps in a darkened aquarium produce any mus- 

 cular responses. 5". davisi differs in this respect from Ccrian- 

 thns mcmbranaceus and Edwardsia lucifuga, according to Nagel 

 ('94, p. 545). 



The responses of anemones to mechanical and chemical stim- 

 uli have been investigated already by Pollock ('82), Loeb ('91 

 and '95), Nagel ('92, '94^, '94^) and Parker ('96). With most 

 of the conclusions of these investigators my own observations 

 accord. I must differ with some, adding also a few facts which 

 to my knowledge, have not been published heretofore. 



Two quite distinct reactions, usually follow the stimulation of 

 a tentacle of 5. davisi by means of a slight touch with a needle 

 or glass rod. The first is a bend at and toward the point of 

 stimulation, whether the latter be near tip or base, on right side 

 or left, above or below, and appears to be due to the response of 

 the muscles involved to a direct stimulus. The second is a con- 

 traction of the whole tentacle, with a simultaneous bending of the 

 tentacle toward the mouth. Evidently all the longitudinal mus- 

 cles of the tentacle not previously active are indirectly excited to 

 produce this reaction, those on the inner (upper) side between 

 base and point stimulated contracting more strongly than the 

 outer (lower) muscles. This unequal contraction is probably to 

 be explained by the greater strength of the inner muscles, which 

 play the greater part in the chief work of the tentacles carrying 

 food to the mouth. The hydroid Corymorpha shows this inequal- 

 ity still more strikingly ; the first reaction of S. davisi is en- 

 tirely wanting and the outer muscles are in use only when the 

 tentacles are slowly returning to their expanded condition after 

 a contraction. But I have been unable to demonstrate histolog- 

 ically any difference in size between outer and inner muscles, 

 in either animal. 



