Chap. VI.l THE NERVOUS SYSTEM OF ARTHROPODS. 95 



and in front of the optic nerves ; whilst nearer the middle 

 line two other nerves on each side (b) are in relation 

 with the palpless mandibles. The thick oesophageal 

 cords (g) are continued from the posterior and inferior 

 angles of the brain ; and, as they descend to enter the me- 

 dullary or sub-oesophageal ganglion at the commencement 

 of the ahdominal cord (i, i), they are united by a cross 

 branch, as in many Crustacea (fig. 36). From this sub- 

 oesophageal ganglion large nerves are given off on each 

 Bide (h) to supply the maxillae and other parts about the 

 mouth. 



" The stomato-gastric nerves, which arise from the 

 posterior part of the brain immediately, form a third 

 slender ring (e) about the oesophagus, from the middle of 

 the upper part of which the trunk of the stomato-gastric 

 system (/) is continued a short way back upon the stomach," 

 when it divides into two branches which " bend abruptly 

 backwards, and run parallel with each other along the 

 dorso-lateral parts of the wide and straight alimentary 

 canal." (Owen.) 



In the more powerful predatory Myriapods, of which 

 the common Centipede may be taken as a type, a distinct 

 advance is met with. This carnivorous creature has a 

 smaller number of better-developed limbs, and its nervous 

 system closely resembles that found amongst the larvae or 

 Caterpillars of higher Insects (fig. 39). The supra-oesopha- 

 geal ganglia, or brain, receive nerves from the two pairs of 

 antennas, and from the groups of ocelli on each side of the 

 head. They are connected by oesophageal cords with a 

 bilobed infra- oesophageal ganglion, which distributes nerves 

 to the jaws and other parts about the mouth. This bilobed 

 infra-cesophageal ganglion is the first and largest of a 

 series of ventral ganglia, numbering about twenty, wliicli 

 are connected together by a double ventral cord. Every 



