Sensory Discrimination: the Chemical Sense 69 



common stem, food and contact stimuli do not produce dif- 

 ferent reactions, but have different degrees of efficiency in V 

 bringing about response. When a grain of sand was placed in 

 contact with the tentacles on one side and a bit of meat in a 

 corresponding position on the other side, the reaction was 

 almost invariably in the direction of the meat. Filtered meat 

 juice allowed to flow upon the distal tentacles produced a reac- 

 tion 82 per cent of the time, while carmine water was effective 

 only 15 per cent of the time. Further, if the distal tentacles 

 were touched several times with a needle, they remained 

 closed ; but if the second stimulus used was a piece of meat, 

 the tentacles opened out and waved about (319). Whether 

 in such a case as this the possible conscious accompaniments 

 of the responses are to be regarded as qualitatively different /f 

 sensations, or only as different degrees of intensity of the same 

 sensation, it is difficult to say. Another hydroid, Corymorpha 

 palma, gives no response whatever to meat juice; only irri- 

 tating chemicals produce reactions, whose character appears 

 to be tactile (402). 



In the sea- anemones or actinians we find behavior in re- 

 sponse to food stimulation as distinguished from contact 

 stimulation varying in different representatives of the group. 

 Generally speaking, the food reaction seems to be more marked 

 than the contact reaction. W. H. Pollock a number of years 

 ago reported his observation that certain unnamed sea- anem- 

 ones opened out if food were suspended near them in the 

 water, and referred the phenomenon to "a sense of smell" 

 (343). Adamsia rondeleti winds its tentacles around bits 

 of sardine meat and passes them from tentacle to tentacle 

 toward the mouth. When balls of filter paper softened with 

 sea water are substituted, the feeding reaction is wholly lack- 

 ing. Either the tentacles fail to react at all, or the ball is 

 "felt of " slowly with no attempt to seize it, or it is momentarily 



