MORPHOLOGY OF BRAIN AND SENSE ORGANS OF LIMULUS. 9 



in eating, but the chelicerae move rapidly back and forth, 

 making frantic snapping movements toward the mouth, as 

 though to pick away some disagreeable object. These move- 

 ments usually last a long time. If wads of blotting-paper 

 wet in ammonia or picric acid are used the chewing movements 

 are reversed, and the offensive object is sometimes snapped up 

 by the chelicerse and rejected. 



Holding strong-smelling food as close as possible to the 

 mouth or to the jaws produces no effect, although chew- 

 ing movements are instantly produced when the jaws are 

 touched by it. 



When a very small piece of clam or of pecten is touched to 

 the surface — say of the third mandible on the left side — care 

 being taken not to touch any other parts, that leg will be 

 promptly raised and the tip bent toward the mouth ; it soon 

 falls back on to the cephalo-thorax again, and then its man- 

 dible moves back and forth, alternating with the leg movement, 

 as in eating; but all the other mandibles and appendages 

 remain quiet. One may start in this way one appendage after 

 the other (except the chelicerse, which have no mandibles), 

 until all of them, first on one side and then on the other, are 

 working in perfect rhythm. 



If the mandibles of the post-oral appendages on one side 

 are stimulated, the chelicera of that side, although not stimu- 

 lated itself, soon has its tip extended straight backward as 

 far as it can reach, and may remain some time in this rigid, 

 unnatural position ; or else it begins those characteristic back 

 and forward movements, snapping its chela from time to time, 

 as though to seize something and lift it up, or else thrusting 

 the chela down the mouth as though forcing some piece of food 

 into the oesophagus. If the jaws on the opposite side are now 

 stimulated, the chelicera of that side begins to work also. It 

 is a curious fact that the chelicerse rarely move when the 

 mandibles of the second or third appendages are stimulated ; 

 not till the last one or two pairs of mandibles are set in motion 

 do they begin their characteristic movements. It is evident 

 that the chewing movement produced in these various ways 



