Bell, Reactions of Crayfish. 31 1 



otaxis that was surprising when compared with their behavior 

 toward a bit of meat itself. The contrast was doubtless due to 

 the fact that here the stimulus was applied directly and in a con- 

 centrated form. As soon as any considerable quantity of the 

 juice diffused through the water to the animal, the latter would 

 face about and move toward the source of the stimulus, making 

 vigorous chewing movements with the maxillae. Fifteen animals 

 were subjected to systematic tests for their response to meat juice, 

 and each animal was stimulated in eleven different places, with 

 the following results: 



(i) The distal portion of the antennae. Reactions were ob- 

 tained from twelve out of the fifteen animals. The typical reac- 

 tions were a slight movement (usually a quick jerk) of the antenna, 

 vigorous chewing movements of the mouth parts, and in seven 

 cases the quick orientation of the animal so that the mouth parts 

 came in contact with the stimulus. In one case there was a vig- 

 orous snapping with the chelae toward the source of the stimulus. 



(2) The ends of the chelae. Here the reactions were very 

 prompt and decided. All the animals reacted except one. The 

 typical reaction was an energetic grasping with the chela toward 

 the source of the stimulus, accompanied frequently by chewing 

 movements, and bringing the chelae and first chelipedes to the 

 mouth as if they held a bit of meat. In five cases the animal 

 brought the mouth to the stimulus. 



(3) The antennules. All but two animals responded, though 

 the reactions were in general not so vigorous as those from the 

 chehe. The chief reactions w^ere twitching the antennules, 

 dropping the antennule stimulated and drawing it through the 

 maxillipedes, in eight cases approach of the mouth to the stimulus, 

 in three cases chewing movements and in two cases snapping 

 with the chelae. 



(4) The mouth parts. Here of course the typical reaction 

 was the chewing movements. These occurred in every case and 

 were usually very vigorous, the animal frequently becoming quite 

 excited. In five cases the chewing movements were accompanied 

 by movements of the chelae and chelipedes to the mouth with a 

 sort of ,sweeping or scraping movement, as though they w^ere 

 scraping up food from the bottom of the vessel. In three cases 

 there was a forward movement as if to come into closer contact 

 with the stimulus. 



