CHAPTER IV. 



NERVE SYSTEM. 



Ganglionic Chain — Supra-cesophageal Ganglion — Reflex 

 Action — Commissural Fibres — System of Larva and 

 Imago — Coalescence and Atrophy of Ganglia — 

 Cephalic Ganglia — Convolutions — Pedunculated 

 Bodies of Dujardin —Relation of Size of Brain 

 to Intelligence — Inferiority of Queens — Stomato- 

 Gastric and Sympathetic Systems — Variety of 

 Nerve Work. 



The nerve system in insects (A, B, Fig. n), 

 whether in the larval or adult stage, consists mainly 

 of a series of rounded masses of brain-like substance, 

 arranged in the median line of the body, near to the 

 lower, or ventral side. These masses, called ganglia* 

 are united by two threads, seen in the figure, and 

 each of which is shown by the microscope to con- 

 sist of a sheath, having within it an immense number 

 of nerve fibres, serving to bring the separate ganglia 

 into union, by carrying impressions received by one 

 to all the rest. The front mass of all is not on the 



* Greek. yayyXlOV, a knot, or excrescence. 



