l6o S. J. HOLMES AND E. S. HOMUTH. 



merited with and showed marked responses from the mouth parts 

 and chelipeds. When the chelipeds were rubbed with a piece of 

 filter paper the substance was seized but rejected if passed to the 

 mouth parts. When meat was pressed against the cheHpeds in 

 the same way it was seized more eagerly, produced a greater de- 

 gree of excitement and was generally eaten. To make sure that 

 this was not due to a difference in the consistency of the two 

 articles two wads of filter paper were taken upon one of which 

 was pressed some meat juice. The two wads were applied to the 

 chelipeds in the same way, but the one with the meat juice was 

 more quickly seized and was generally passed to the mouth parts 

 and swallowed. In some instances the pure filter paper was 

 swallowed, but this was very rare. 



The chelipeds were also stimulated simultaneously, the one 

 with pure filter paper, the other with filter paper soaked in meat 

 juice. The animal almost invariably turned toward the side with 

 the meat juice and grasped more vigorously on that side. The 

 stimuli were frequently transposed but this did not affect the 

 result ; the reaction to the paper with the meat juice was the more 

 vigorous. 



In one crayfish the nerve cord was cut across directly behind 

 the mouth parts and in front of the large chelipeds. The result 

 of this operation is to somewhat paralyze the animal, especially 

 the anterior chelipeds which are drawn up under the body. Ob- 

 jects that touch the chelae are frequently passed to the mouth 

 but again rejected. A bit of meat, however, is chewed and swal- 

 lowed although this act requires a much longer time than in the 

 normal animal. In some cases the chewing movements ceased 

 before the food was swallowed. The chelipeds when stimulated 

 by meat grasp it more eagerly than they seize innutritions mate- 

 rials, and the animal in general shows a greater degree of ex- 

 citement. 



The experiments recorded show that the outer ramus of the 

 antennules which bear the so-called olfactory setse are especially 

 sensitive to olfactory stimuli ; that the inner ramus of the anten- 

 nules and the antennae are also sensitive to olfactory stimuli but 

 to a less degree ; and that the olfactory sense is developed in other 

 parts of the body, especially the mouth parts and tips of the 

 chelipeds. 



