34 



The Form of Insects 



jm.g. 



oesophageal ganglion are united into a single mass 

 situated in the fore-body (2, 4). Such fusion of 



nerve-centres may 

 -f^-9- be said to result in 



concentration of in- 

 dividuality; for 

 where a nerve - 

 centre is present in 

 each segment, each 

 segment is to some 

 extent capable of 

 independent life. 



In addition to the 

 nerves and nerve 

 masses of the 

 central chain, there 

 is in insects a set of 

 nerves associated 

 with the front part 

 of the food-canal. 

 In the Cockroach a 

 pair of nerves pass 

 forwards from the 

 nerve-ring around 

 the gullet, above 

 which they unite in 

 a three - cornered 

 nerve-centre 

 (^frontal ganglmi). 

 Thence a pair of 

 small nerves run 

 downwards to the 

 upper lip, while a 

 central (recurrent) 

 nerve passes back- 

 wards along the gullet to a triangular nerve-centre ] 



Fig. 26. — Stomato-gastric-nerves of Cockroach. 

 fr. g. frontal ganglion ; at. nerve to feeler; 

 conn, connective •,pa.g. paired ganglia ; r. n. 

 recurrent nerve ; v. g. ventricular ganglion. 

 Magnified. From Miall & Denny. 



