MORPHOLOGY OF BRAIN AND SENSE ORGANS OF LIMULUS. 37 



Exp. B. — Cutting across the ventral cord just back of 

 the chelaria causes regular raising and lowering of the abdo- 

 minal appendages about twenty times a minute. They finally 

 come to rest, and are then left in an unnatural position, with 

 the right and left appendages of the same pair crossed over the 

 median line. The mandibles are pressed firmly together in a 

 sort of tetanus, the line of the meeting being irregular and un- 

 symmetrical. Strangely enough, stimulation of the mandibles 

 with food produced, in this instance, no regular movements of 

 mastication. But a warm hand placed on either side of the 

 cephalo-thorax produced immediate and simultaneous move- 

 ments of the legs of both sides. The temperature reaction 

 of the cephalo-thorax, then, is apparently not in- 

 fluenced in the least by section of the ventral cord, 

 but the respiratory, and perhaps the gustatory re- 

 flexes are strangely affected. 



Exp. C. — In this experiment the crab operated upon had 

 already had the mandibles belonging to the second right appen- 

 dage removed, but was otherwise in perfect condition. A deep 

 median longitudinal cut was made, severing (as shown by 

 post-mortem examination) the post-oral cross-commissures of 

 the crura, and cutting through the junction of the crura in the 

 vagus region (PL 4, fig. 48). The animal lived nearly two 

 months in apparently good condition. It was then killed to 

 make sure of the direction of the cut. During this period it 

 ate with the normal movements of the mandibles, except that 

 they worked perhaps a little more slowly than usual, and the 

 chelicerae were not brought into action. On placing the 

 warm hand on one side of the cephalo-thorax of the 

 quiescent animal, responsive movements of the legs 

 on both sides were at once produced. The tempera- 

 ture reaction was unaffected. 



Exp. D. — In this specimen the crus of the left side was sec- 

 tioned just back of the second pair of legs. The results were 

 very clearly marked. After about five hours, when the crab 

 had become perfectly quiet, placing the hand anywhere on the 

 left side of the cephalo-thorax produced no movements what- 



