THE NERVOUS SYSTEM OP THE LOBSTER. 319 



the body and appendages). But the effects were much less marked 

 than in the case of E. The reflex divaricator action on stimulating 

 the central end of the large nerve was slight. The reflex closing of 

 the claw on stimulating the central end of the small nerve, however, 

 was distinct, and the effects on stimulating the distal end of each 

 nerve the same as usual. The animal in this case was soon exhausted. 



This experiment shows that the second thoracic ganglion acts as a 

 special reflex centre for the great chelae ; since the reflex closing and 

 opening of the claw on stimulating the central end of the small and 

 large nerve respectively take place when it is isolated. This is pre- 

 sumably the case with the other thoracic ganglia. 



Yung came to a similar conclusion with regard to these ganglia ; he 

 says: — "Chaque ganglion est un centre de sensibilite et de mouve- 

 ment pour le segment du corps auquel il appartient ; mais la sensi- 

 bilite" est inconsciente et les movements reflexes lorsque le ganglion 

 est separe' de ceux qui le precedent" (pp. 492, 493). "Les gan- 

 glions thoraciques se comportent comme les ganglions abdominaux 

 pour les membres de leur segment respectif. Leur destruction en- 

 traine l'abolition des mouvements volontaires dans les appendices 

 situes en arriere " (p. 525). These results were obtained chiefly by 

 cutting the chain at various points and observing the subsequent 

 effects. 



2. The .Nerves in the Ambulatory Limbs. 



Experiments on the nerves in the other ambulatory limbs were not 

 carried on in the same detail as in the case of the chelae, for the reason 

 that the nerves are much more difficult to expose. 



On stimulating either nerve movements took place in the limb and 

 also general reflex movements of the body and appendages ; the latter 

 movements being strongly marked in the case of the large nerve, but 

 slight when the small nerve was stimulated. When the large nerve 

 was stimulated the limb as a whole was flexed, and extended when 

 the small nerve was stimulated. 



Thus each nerve is mixed as in the case of the chelae. 



3. The Abdominal Nerves. 

 The nerves arising from one of the abdominal ganglia were exposed 

 and cut. Sharp flapping of the abdomen took place when the central 

 end of either nerve was stimulated, but the effects were stronger in 



