388 Introduction to Animal ]\lorphology. 



Besides this nerve system there are three series of 

 visceral nerves : First, symmetrical, lateral, sympathe- 

 tic nerves arising from the back of the brain ganglion, 

 and running on the side of the oesophagus, forming 

 one, two, or many ganglia thereon. Second, the ncmts 

 recitrrcns, a medial nerve, arising from a small trian- 

 gular single, rarely double or triple (occasionally) 

 ganglion frontale^ anterior to the epipharyngeal gan- 

 glion (from each side of the front of which its roots, 

 the nervi vagi, spring), passing backwards on the 

 dorsal aspect of the oesophagus, to form a plexus with 

 branches of the foregoing. Third, ncrvi tnvi>- 

 ari si Tig from the upper cord of the ventral nerve chain; 

 each of which divides into two branches in front of 

 each ganglion, r branches of communication 



from the foregoing, and supplies the tracheae and the 

 muscles of the stigmata. In development the i 

 system is comparatively late in being differentiated 

 from the tissues around it. The nerves terminate in 

 distinct Di-\\ f rean eminences in muscles, often in touch 

 rods, or hair-like free ends on the surface. 



The antennaD are abundantly provided with touch 

 corpuscles, which also exist on the palps and tarsi. 

 Short conical bodies on the front of the antennae may 

 be organs of smell.* Hearing organs are not uni- 

 versal, but the antennary rods of graduated lengths 

 have been shown to vibrate in response to certain 

 musical sounds ; some have a chitinous ring, over 

 which is stretched a drum-like membrane ; beneath this 

 is a trachea dilated into a vesicle, on which is seated 



* Or the fine pores on the antennae of Lamellicornes (Erichson], or the 

 Stigmata ? (Cuvicr). 



