Sensory Discrimination: The Chemical Sense 71 



the adaptive aspect that the starved animal can afford to 

 lose no chances, and suggests the analogy from our own 

 experience of the loss of intellectual discrimination in mo- 

 ments of intense emotion. For the emotion too repre- 

 sents a situation where the organism cannot afford to lose 

 chances by hesitating in reaction long enough for nice 

 discrimination. 



In Tubularia crocea, a ccelenterate belonging to the family 

 of hydroids which form colonies of many individuals on a 

 common stem, food and contact stimuli do not produce 

 different reactions, but have different degrees of efficiency 

 in 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 reaction 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 (564). Whether in such a case as this 

 the possible conscious accompaniments of the responses are 

 to be regarded as qualitatively different 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 irritating 

 chemicals produce reactions, whose character appears to 

 be tactile (714). 



In the sea-anemones or actinians we find behavior in 

 response to food stimulation as distinguished from contact 

 stimulation varying in different representatives of the 

 group. Generally speaking, the food reaction seems to 



