102 INSTINCT 



instincts of the animal are by no means monopolized by the 

 brain, but that the various ganglia of the ventral nerve cord 

 are the controlling centers of many activities. If we cut 

 the commissures connecting the brain with the chain of 

 ventral ganglia, the reactions of the eyes and antennae take 

 place in the usual way. If the eye stalk is stimulated it is 

 withdrawn; if the antennules or antennae are touched they 

 are drawn back, but there is no reaction from the legs. On 

 the other hand, if a leg is seized an effort is made to with- 

 draw it; if this is not successful other legs may be employed 

 to push against one's hand or the chelipeds may reach over 

 and pinch the offender. The crayfish can walk in the usual 

 manner, and when placed in the water it can swim as well 

 as a normal individual. Its movements are more restless 

 than before, owing to the lack of inhibitory impulses which 

 under ordinary circumstances are issued from the brain. 

 Food is seized by the chelipeds, passed to the mouth parts, 

 chewed and swallowed; if stones or other innutritious objects 

 are presented to the mouth parts they are at once rejected, 

 showing that connection with the brain is by no means 

 necessary for the proper discrimination of food. 



If the commissures are cut farther back, between the sub- 

 esophageal and the first thoracic ganglia, power of moving 

 the legs still remains, although locomotion is somewhat 

 impeded. If a leg is seized it is withdrawn or defended by 

 the other appendages. Pieces of meat or paper given to the 

 chelipeds are passed from one to the other and pressed 

 between the mouth parts where they may be seized and 

 swallowed. Often the mouth parts are tardy in responding, 

 aad the chelipeds may vainly persist for hours in pressing 

 the object against them. Sometimes bits of food are torn 

 to pieces and then offered to the mouth parts. Stones or 

 other hard objects are not passed to the mouth, and if seized 



