THK NERVOUS SYSTEM. 77 



most easily observed in the living insect when it first 

 emerges from the pupa. When removed from the abdomen 

 the folds of the elastic coat are easily obliterated, unless it is 

 first hardened in a solution of chromic acid. 



Section XI. The Nervous System. 

 PLATE VI., Fio. 1, AND PLATE VII., Fias. 1 1 AND 10. 



The parts of which the nervous system is composed have 

 already been indicated.* The cephalic nerve centre will be best 

 described by describing its component ganglia. These are three 

 pairs, which I shall name the central or antennal, the anterior 

 or cerebroid, and the lateral or optic ganglia. 



The great thoracic nerve cord forms the lowest portion of 

 the cephalic nerve centre, and when seen from beneath appears 

 as a somewhat lozenge-shaped flat surface, from the anterior 

 portion of which the great nerves of the probocis arise. These 

 appear to be chiefly composed of fibres from this cord. A pair 

 of crura arise from the upper side of the thoracic cord, and 

 diverge to allow the oesophagus to pass between them ; these 

 enter the cephalic nerve centre where their fibres spread out, 

 and connect the different ganglia of which it is composed. 

 The tracing of these is exceedingly difficult, but I believe 

 I have clearly made out, that a large bundle extends to each 

 optic ganglion, that another set chiefly run up the back of the 

 central ganglia, whilst others accompany the oesophagus, and 

 appear anteriorly as a pair of small nerves, upon which the 



* Page 13. 



