314 yoiirnal of Cojnparative Neurology and Psychology. 



the reception of chemical stimuH. More decided and definite 

 responses were obtained from the chelae, the mouth parts, and 

 the first and second chelipedes. There was one characteristic 

 reaction, however. The antennule stmiulated was frequently 

 lowered to the mouth, clasped by the third maxillipedes, and 

 drawn up through them. Could we hazard the guess that the 

 antennules are a sort of outpost for chemical stimuli, and that 

 when stimulated they are brought to the mouth in order to give 

 the animal opportunity to examine the substance more carefully ^ 

 If so, it cannot be because they are more sensitive than the "anten- 

 nae and chelae but only more mobile. On the other hand, the 

 action may be merely a wiping reflex to clean the organs of the 

 stimulating substance. The most sensitive appendages are de- 

 cidedly the first and second chelipedes. The general tendency 

 of the reactions was unquestionably to bring the animal into more 

 of the stimulus, in other words a marked positive chemotaxis to 

 meat juice was exhibited. 



2. Lavender Water. — As stated above, Nagel experimented • 

 on crayfish with lavender water, and interpreted the dropping of 

 the antennules as an indication of a disagreeable experience. In 

 view of the reactions already observed, this interpretation is 

 scarcely justified. A series of experiments was made on five 

 animals in each of the eleven regions mentioned above to deter- 

 mine their exact reaction to lavender water, (i) Three out of 

 the five reacted to the stimulus on the antennae, one by removing 

 the part stimulated, two by backing off from the spot. (2) Four 

 responded to stimulation of the chelae, one by removing the mem- 

 ber, three by withdrawing from the place. (3) From the anten- 

 nules there were four responses out of five, three being movements 

 away from the stimulus, and one drawing the antennule through 

 the maxillipedes. (4) Four animals reacted when the mouth 

 parts were stimulated, one with a slight movement, three with a 

 vigorous fanning by the filamentous endopodites of the maxillipedes. 

 This fanning set up a decided current from behind forward which 

 tended to carry the substance away from the mouth parts. Along 

 with this in two cases there was a vigorous pushing outward and 

 forward with the first and second chelipedes and the maxillipedes, 

 as though to ward off and push away the substance. In no case 

 were any chewing movements noticed. (5) All five animals 

 responded very vigorously to stimulation on the first chelipedes, 



