468 



COMPARATIVE ANATOMY 



CHAP. 



centrated in the imago. MyniwUon is, however, a, case of adaptation of the nervous 

 system to the short compressed form of body of the larva. 



Jiti nrd 



Fig. Sir.. — Median longitudinal section tlirough tlie head of Blatta orientalis. The nervous 

 system of the head is drawn entire. Tiyp, Hypopharynx ; os, oral cavity ; Ibr, upper lip ; gf, ganglion 



frontale ; g, brain ; na, root of the antennal nerve ; 

 710, root of the optic nerve ; ga, anterior ; gp, pos- 

 terior ganglion of the paired visceral nervous system ; 

 oe, o?sophagus ; c, cesophageal commissure ; usg, 

 lUV infra-cfisophageal ganglion ; cc, longitudinal commis- 

 .1,, sure between this and the first thoracic ganglion; 

 sg, common duct of the salivary glands ; Ih, lower 

 ^^^ lip = 2d pair of raaxillte ; nr, nervus recurrens ; d, 



nerve uniting the frontal ganglion with the ceso- 

 phageal commissiu-e ; e, nerve from this commissure 

 to the upper lip ; /, nerve from the infra-03S0phageal 

 ganglion to the mandible ; g, to the anterior max-. 

 illEe ; li, to the lower lip (after Bruno Hofer). 



(5) In many oases where in the larva 

 there is an apparently concentrated ventral 

 chord, its ganglia are quite distinct although 

 lying very close together. In the imago 

 they separate and the longitudinal commis- 

 sures become distinct, so that a non- con- 

 centrated or less concentrated imaginal 

 nervous system is developed. 



The sympatlietio nervous system seems 

 to be present in all Antennata. It consists 

 of an unpaired and a paired system. In 

 Blatta, whose visceral nervous system (Figs. 

 326 and 327) has been the most investigated, 

 PiG.827.— Anterior portion of the paired the unpaired portion shows the following 

 and unpaired visceral nervous system of ^^^.^^„^^^^t. In front of the brain on the 

 Blatta orientalis, seen from above. The ° ,, ,. . , 



outlines of the brain fe) and the roots of the cesophagns there lies an unpaired ganglion 

 antennal ner\'e (ma), which cover a portion of frontale gf, which gives off nerves to the 

 the sympathetic nervous system, are given by upper lip and the cesophagns. It is con- 

 dotted lines. Lettering as in Fig. 326. nsd, ^^^^^^ , ^ ^^^^^ ^^ ^^^-^^ gj^g ^^.^^^ ^^^ 

 Nerve to salivary-gland. The nervus recurrens ' -, i ■ c i ■ -u ii, 



,r) enters an unpaired stomach ganglion esophageal commissure, from which another 



{nr) 



further back (after Bruno Hofer). 



nerve as well goes off to the ossophagus and 



