158 



S. J. HOLMES AND E. S. HOMUTH. 



on the reactions. All of the specimens were kept for the same period 

 without food, were placed in the same kind of dishes and treated 

 in all respects as nearly as possible in the same way. Only indi- 

 viduals which had been resting quietly for some minutes were 

 employed for experiment. If any reaction was produced by the 

 movements of the observer the crayfish was not used for experi- 

 ment until it had been left for a considerable time and became 

 perfectly quiet. A piece of meat was very carefully introduced 

 into the water with a long fine forceps and held a quarter of an inch 

 above the rostrum. If one's movements are exceedingly slow it 

 is possible to work around crayfish even when recently brought 

 in from the field without exciting alarm. The number of seconds 

 was noted before any of the feeding responses of the legs or 

 mouth parts were set up. Sometimes such movements appear to 

 arise spontaneously, and therefore only those cases were counted 

 in which these movements eventuated in seizing and devouring 

 the meat. In three sets of experiments performed at different 

 times the time reactions of the crayfish were as follows : 



Outer ramus removed 

 Inner ramus removed 

 Botli rami removed no 

 Normal animal 46 



Outer ramus removed 

 Inner ramus removed 

 Both rami removed 

 Normal animal 



Outer ramus removed 

 Inner ramus removed 

 Both rami removed 

 Normal animal 



Experiment I. 



Time of Reactions in Seconds. 



220 64 

 6 

 58 Il6 

 30 24 



Average. 



74 

 48 



131 

 31 



174 

 27 

 81 



8.7 



25.6 

 23 



167.5 

 22.7 



Experiment IV. 



(Specimens with eyes blackened over.) 

 Outer ramus removed 72 116 180 120 36 94 30 no 144 



Inner ramus removed 

 Both rami removed 



42 



4 



112 



4 

 242 



4 

 270 



36 12 4 



100 



14 13-7 

 I4I-S 



