NERVOUS SYSTEM. INVEHTEBRATA. 23 



of the latter view, it may be said that the globuli of Crusta- 

 ceans agree with the antennary lobes of Insects in having 

 giomerular condensations o their neuropile, in giving off 

 a root to the antennary nerve, and in receiving a large 

 decussating tract from the fungiform body of the opposite 

 side, assuming such to be the nature of the protuberance 

 on the optic ganglion of the Lobster. 



The tritocerebrum constitutes the centre for the second 

 antennary and the tegumentary nerves. 



The complicated structure of the cerebral ganglion is 

 apparently mainly due to its connection with highly 

 developed sense-organs, yet the fact that its removal causes 

 more disturbance to the normal activities of the creature 

 than in Worms particularly by destroying the capability 

 of spontaneous locomotion suggests that it possesses to 

 some degree, at any rate, the power of controlling, or 

 perhaps even of initiating-, activities in the rest of the 

 nervous system. 



A pair of small ossophageal ganglia are situated upon 

 the circumoesophageal connectives on a level with the 

 oesophagus, but some distance in front of the post- 

 oesophageal commissure by which they are united. 



Each of them gives off, besides a few delicate filaments 

 to the oesophagus, two stout nerves. One of these runs 

 forward, parallel to the oesopbageal connectives, half-way 

 to the cerebral ganglion, and at this point unites with its 

 fellow of the opposite side and with a median nerve derived 

 from the cerebral ganglion, to form the gastric nerve a 

 trunk that runs in the median plane along the anterior and 

 dorsal surfaces of the stomach to the pylorus, at which 

 point it forms a small ganglion and divides into two lateral 

 branches which are distributed to the intestine. The second 

 of the two nerves supplies the upper lip and is connected by 

 a branch to the components of the gastric nerve where they 

 unite to form the median trunk. The suboesophageal 

 ganglion innervates the mouth appendages and gives off 

 from its dorsal surface a few nerves to the body -muscles ; 

 it is composed of six pairs of ganglia fused together. The 

 removal of this ganglion occasions [in the Crayfish (Astacus 

 ftuviatilis)^ the loss of all power of co-ordinated locomotion, 



