Bell, Reactions of Crayfish. 317 



chelae and chelipedes with acid I cannot conjecture. Sometimes 

 when the stimulus was on the outer and under portion of a chela 

 the contortions of the animal in its efforts to get the spot up to the 

 mouth were violent and even grotesque. Both this and the re- 

 action to the spot on the carapace indicate a tolerably definite 

 localization of chemical stimuli. 



^. Hydrochloric Acid. — Nagel, as already mentioned, states that 

 when Astacus was stimulated with a i per cent, solution of this acid 

 the animal wiped its antennules, then its antennae, and finally but 

 invariably its eyes with its maxillipedes and chelipedes. This 

 action was thought to indicate pain. Nagel does not indicate 

 in detail the method of experimentation and it is probable that no 

 great care was taken to stimulate particular portions of the animal, 

 and from what we have already learned regarding reactions to 

 acetic acid we can say that the reactions he describes are those we 

 would expect from a general stimulation of the whole anterior 

 surface. To get more accurate data on this point five animals 

 were tested in the manner indicated above with a i per cent, solu- 

 tion of hydrochloric acid, (i) Antennae. Four animals out of 

 the five responded. The most marked response was a quick move- 

 ment of the organ away from the stimulus. In one case there was 

 a quick spreading of the chelae as if for the attitude of attack, in 

 another the animal faced sharply about tow^ard the stimulus, and 

 in a third the antennules were wiped by the maxillipedes as the 

 animal moved off. In no case were the antennae wiped or rubbed. 

 (2) Chelae. All the animals reacted, two by springing away from 

 the stimulus, two by snapping the forceps of the chelae and in one 

 case bringing the chela to the mouth and accompanying the action 

 with chewing movements, and one by drawing the antennules be- 

 tween the maxillipedes. (3) Antennules. Three animals drew 

 the member through the maxillipedes, one avoided the stimulus, 

 and one grasped with the chelae and made vigorous chewing move- 

 ments. In two cases the animal faced about to the stimulus, and 

 in one case even seizedthe pipette in its forceps — a thing which had 

 not occurred before. (4) Mouth parts. The reactions were very 

 vigorous in all cases. The chewing movements were naturally 

 the most striking, these being violent in all cases but one. That 

 one animal merely sprang away from the stimulus. In three cases 

 there was grasping with the chelae and chelipedes, in two the mouth 

 was rubbed by the chelipedes, and in one the animal faced about 



