KWING : OBSERVATIONS ON ACRTDIDyE. 313 



quence of the unsjmmetrical posture of the appendages, the 

 animal moves in a circle. 



III. Extirpation of thbc Subcesophageal Ganglion. 



Removal of the suboesophageal ganglion is attended with 

 much difficulty, but with great care it was removed without 

 loss of much blood. The wound was closed with shellac. The 

 loss of this ganglion does not stop the respiratory movements. 

 The respifatory centre is therefore not located in this part of 

 the nervous system, which is therefore not analogous to the 

 medulla in vertebrates, as Faivre and others maintained. The 

 spiracles of the abdomen and thorax continue their activity at 

 a slower rate, and, as in the normal animal, the abdominal and 

 thoracic spiracles often do not keep the same rhythm. More- 

 over, some of the spiracles on one side of the thorax may be 

 motionless, while those on the opposite side are active. This 

 is explained by the fact that each half of the ganglion inner- 

 vates its own side of the body. The relation, however, between 

 the two halves is so intimate that they usually act together in 

 producing ordinary movements. The palps remained motion- 

 less ; when they were strongly pinched they did not respond. 



Shortly after the operation the head droops and touches the 

 table, and the antenna may remain in the position in which 

 they are placed, e. g., one pointing anteriorly and the other 

 posteriorly. It hops but does not walk unless it is irritated. 

 It remains for about an hour in any position in which it is 

 placed, after which the shock effect passes off. If any part 

 of the thorax or abdomen is pinched, reflex movements of the 

 different parts posterior to the injury are observed, but no re- 

 flexes of parts anterior to the cut follow. It moves spontane- 

 ously after two hours, dragging its body along as if it were a 

 heavy load. Its first pairs of walking-legs are abnormally 

 flexed, and therefore do not coordinate in a normal manner 

 with the others. This is because their nerve fibers were injured 

 or stimulated by the operation. If it meets an obstacle it may 

 fall over on its side, but immediately, though awkwardly, rights 

 itself. In all the movements there seemsto be a lack of perfect 

 coordination for at least twenty-four hours. 



Faivre believes, from his experiments on Dytiscvs, and Ward 

 from those on the crayfish, that the suboesophageal ganglion is 



