Bell, Reactions of Crayfish. 325 



experiments will not be given. When the piece of vegetable was 

 suspended in the water it occasioned no restlessness of the animals, 

 such as was produced by meat. Even when it was held within a 

 centimeter of the antennules there was no response unless it hap- 

 pened to be touched by an antenna. As soon as it was touched 

 to any part of the body, even the telson, the animal responded 

 vigorously, seized the bit accurately and devoured it greedily. 

 The gusto with which the animals chewed at and devoured the 

 vegetables was even greater than that exhibited with meat. Onion 

 especially seemed to be a favorite delicacy. 



SUMMARY. 



1. Crayfish react to meat juice very quickly and definitely with 

 a positive chemotaxis. To lavender water, acids and salt the re- 

 actions were rather indicative of a negative chemotaxis. The 

 reactions to sugar and quinine were on the whole less definite, and 

 quinine in general seemed to have a quieting effect upon the 

 animals. 



2. The animals react to chemical stimulation on any part of 

 the body, and therefore we must assume that there are chemical 

 sense organs all over the body, just as in some fishes. Neverthe- 

 less for all stimuli the anterior appendages show the greatest sensi- 

 tiveness, either because they are better supplied with chemical 

 sense organs or because these appendages are more used in food 

 getting. 



3. There is no evidence that the antennules are specialized 

 organs for the reception of chemical stimuli. It is true that the 

 characteristic reaction of those organs is dropping to the mouth 

 and being wiped by the maxillipedes, but more definite and more 

 vigorous reactions were obtained from stimulation of the mouth 

 parts and the first and second chelipedes. 



4. There was a rather definite localization of the stimulation, 

 as indicated by rubbing the outer portion ot the chela, pulling at 

 the abdominal appendages, digging at the eyes, and scratching 

 and grasping at a limited spot on the carapace. 



5. When the abdominal appendages were stimulated with meat 

 juice some of the animals bowed up on the telson and made as if 

 to pass the stimulus along to the mouth with the chelipedes. 

 Stimulated with acid or salt the pleopods were merely pulled or 

 scraped. 



