Bell, Reactions of Crayfish. 321 



In the case of one animal, however, the stimulation of the third 

 chelipedes on either side called forth the characteristic flight reflex 

 caused by the sudden flexing of the abdomen. (9) To stimulation 

 on the abdominal pleopods all animals responded, four by slowly 

 flexing the abdomen, one by flattening the abdomen on the bottom 

 of the pan and slowly spreading and contracting the telson. This 

 flattening was observed in one other case before the abdomen was 

 flexed. (10) The telson responded in only two animals, and that 

 by a slight folding of the plates on each other. (11) No reaction 

 was gotten from the carapace, except perhaps a slight restlessness 

 in two cases. (12) Three animals reacted to stimulation on the 

 eyes by drawing them in. 



It is evident from all this that the reactions to sugar were less 

 marked and definite than those to the other stimuli thus far used. 



7. Hydrochlorate of Quinine. — In determining the reactions of 

 the crayfish to a bitter substance a 2 per cent, solution of hydro- 

 chlorate of quinine was employed, and five animals were tested 

 in the usual manner. Here the most striking result was the eff^ect 

 of the stimulus upon an active, more or less restless animal. In 

 quite a number of cases such an animal would become suddenly 

 quiet and remain so for as much as half a minute. This was never 

 noted for any of the other stimuli. Aside from this characteristic 

 reaction the responses were usually slight movements. The anten- 

 nules were always lowered to the mouth, but very slowly and in a 

 hesitating manner. When the mouth parts w^ere stimulated the 

 maxillipedes were slowly rubbed together, and in one case the 

 antennules were lowered. None of the chelipedes responded with 

 more than a slight movement. On the abdomen and telson the 

 substance caused a cessation of all movement in four cases, a flex- 

 ure of the abdomen in three, and folding of the telson plates slightly 

 in three. From the carapace there was no reaction that one could 

 be certain of. The most vigorous responses w^ere from the eyes. 

 Four animals reacted to this stimulus, one by slightly twitching one 

 of the eyes, another by withdrawing the right eye but not the left, 

 the other two by first digging fiercely at the eye with the second and 

 third chelipedes, then drawing in the eye but continuing the scrap- 

 ing and digging. 



The results of these experiments with chemicals upon the 

 crayfish are in complete accord with Herrick's observations 

 on the lobster, to the effect that all parts of the body are 



