302 "Journal of Comparative Neurology and Psychology. 



invariably its eyes with the maxillipedes and chelipedes. This 

 action seemed to indicate pain. 



Experiments on Carcinus showed that a piece of meat, held one 

 centimeter from the animal's head, caused a violent movement of 

 the antennules but the meat was not grasped unless it touched the 

 mouth parts. This was no sign of taste, for the same thing oc- 

 curred with tasteless objects. Other reactions went to show that 

 the antennules are organs of touch as well as of taste, a condition 

 which does not seem to prevail in Pagurus and Astacus. Nagel 

 is in doubt as to how much Carcinus is guided by the chemical 

 sense in procuring food. He often saw children catching them 

 with strings without any bait, and thinks they were caught by 

 touch and sight rather than by taste, or at least not solely by 

 taste. In shallow water Carcinus seizes whatever touches or 

 comes near him, but is never observed to hunt up bait at a distance. 



Bethe^ cannot agree with Nagel regarding Carcinus. He 

 thinks that in the search for food it is the chemical sense upon 

 which the animal depends almost altogether, and that the eye 

 plays a very insignificant role. If a Carcinus sees a bit of meat 

 fall into the aquarium, he does not react at all at first and only 

 after some seconds, when the juice has diffused to him through 

 the water, do the antennules begin to wave vigorously. Seven or 

 eight vessels were arranged one above the other with a small 

 Carcinus in each. Water was conducted into the upper vessel 

 and allowed to flow down through the others in succession. If 

 a piece of meat was placed in the upper vessel the animal in the 

 one below^ was seen to grow excited and reach upward, and this 

 was repeated at a definite interval by each of the others in turn. When 

 a piece of meat is thrown into an aquarium the animals begin to 

 move soon after the stimulus reaches them, and proceed in a 

 rather direct line to the food. Blinded animals do the same, even 

 at a distance of half a meter or more. Therefore the chemical reac- 

 tion is of most importance in the search for, food. The mouth 

 parts seem to be more sensitive to chemical stimulation than the 

 antennae or the antennules, since the animals react when the 

 latter are removed. The threshold for chemical stimulation is 

 extremely low, for the animals react vigorously to the trail left in 



^Bethe, Alb. Das Nerv'ensystem von Carcinus maenas, I. Archiv fiir mikroskopische Anatomie, 

 50, pp. 460-547, 589-640. 1897. 



