Bell, Reactions of Crayfish. 303 



the water by a finger that has been in contact with meat, and 

 greedily devour filter-paper which has barely touched meat, but 

 to really clean filter-paper they pay no attention. 



Herrick^ experimented with ammonia gas and clam juice on 

 various parts of the lobster. "All or nearly all the appendages 

 react strongly to chemical stimuli, and in many cases the surface 

 of the body is capable of receiving and responding to stimuli of 

 various kinds." Ammonia gas on the telson sometimes caused 

 violent flexion of the abdomen, on the swimmerets it occasioned 

 scratching movements of the walking legs to remove the disturb- 

 ance, on the mouth parts it produced violent chewing move- 

 ments, and on the back it induced movements of the legs. The 

 walking legs were most sensitive at their tips, and the chelae 

 closed vigorously when stimulated with the gas at the tip. The 

 mouth parts were especially sensitive to clam juice, and active 

 chewing movements were set up. Other portions of the body 

 gave little or no response. It should be noted that Herrick's 

 method of experimentation was the rather crude one of laying the 

 animal on its back on a table, sprinkling it now and then with 

 sea-water, and applying the stimulus directly. 



Dearborn- thinks that the third maxillipedes are the organs 

 of taste in the crayfish since they would sometimes remain 

 extended a few seconds over a bit of meat and then seize it and 

 press it to the mouth. One animal seized and chewed a piece of 

 sheet rubber cut to represent a leech, but none of the rest would 

 notice it. Dearborn also experimented with three odors both 

 in and out of the water but got no reactions whatever. 



Spaulding^ found that the chemical stimulation of Pagurus 

 with fish meat produced a reaction that was sufficiently strong 

 to overcome a marked positive phototaxis, and in connection with 

 the sight of the screen which darkened that portion of the aquarium 

 where the food was placed, set up an association which even 

 without the chemial stimulus was sufficient to overcome the 

 avoidance of the dark. 



'Herrick, F. H. The American Lobster: A Study of its Habits and Development. Bulletin 

 v. S. Fish Commission, VoL 15, pp. 1-252. 1895. 



^ Dearborn, G. V. N. Notes on the Individual Psychophysiology of the Crayfish. American Jour- 

 nal of Physiology, Vol. 3, pp. 404-433. 1900. 



^ Spaulding, E. An Establishment of Association in Hermit Crabs (Eupagurus longicarpus). 

 Journal of Comparative Neurology and Psychology, Vol. 14, pp. 49-61. 1904. 



