3l6 • 'Journal of Comparative Neurology and Psychology. 



When the acid touched the mouth parts three animals jumped back, 

 three rubbed the mouth with the chelae and the first and second 

 chelipedes, two fanned outward with the filamentous endopodites, 

 and one kept up strong chewing movements. In one case the 

 stimulation of the mouth parts caused a convulsive contraction of 

 all the members, followed by an almost total cessation of movement 

 for eight minutes, except for a few slight tremulous grasping move- 

 ments of the first chelipedes. On being put back in the aquarium 

 the animal became active again and a few hours later seemed none 

 the worse for the experience. None of the others were affected in 

 this way. (5 and 6) The first and second chelipedes when stim- 

 ulated were invariably rubbed by the others and wiped by the 

 maxillipedes, and frequently the animals jumped back from the 

 stimulus. Reactions occurred in every instance and were very 

 prompt and decided. (7 and 8) Only four animals responded to 

 stimulation of the third and fourth chelipedes, and the response 

 was a movement of the part away from the stimulus. (9) When 

 the ventral surface of the abdomen was stimulated three of the 

 animals reacted by bowing up on the telson and chelae, rubbing, 

 pulling and clawing at the pleopods with the chelipedes for perhaps 

 as much as a minute. In the case of the other two animals 

 the abdomen was tightly flexed and the animals sprang away. 

 (10) In every case stimulation of the telson caused a quick, 

 strong flexion of the abdomen, and in one case the animal 

 jumped half way across the pan. (11) In two cases the back of 

 the carapace gave no reaction, in two there was a slight restlessness, 

 and in the fifth case the animal reached up and scratched the stim- 

 ulated spot with one of the second chelipedes, a feat which was by 

 no means easy to execute, and the like of which was not observed 

 with either lavender water or meat juice. The same animal, when 

 stimulated on the eye, rubbed the spot vigorously with the second 

 cheliped on that side. This animal was decidedly the liveliest of 

 the lot in all the reactions. Once as it was moving around the pan 

 it came upon a drop of the solution diffusing through the water. 

 Immediately the forceps of the chelipedes closed and were brought 

 to the mouth, the mouth was brought over the stimulus, and de- 

 cided chewing movements were observed, just as if the stimulus 

 had been meat juice. This was the only case where such behavior 

 was observed. 



Why chewing movements should be set up by stimulation of the 



