558 



CLASS II. ONYCHOPHORA. 



_ atn 



ganglia as there are legs. There is in addition a ganglionic 

 enlargement at the commencement of the oesophageal com- 

 missures, where the nerves to the oral papillae are given off 



(Fig. 339, arri). 



The ventral cords are placed 

 each in the lateral compartments 

 of the body cavity, immediately 

 within the longitudinal layer of 

 muscles. They are connected 

 with each other, rather like the 

 pedal nerves of Chiton and the 

 lower Prosobranchiata, by a num- 

 ber of commissures. These com- 

 missures exhibit a fairly regular 

 arrangement from the region in- 

 cluded between the first and the 

 last pair of true legs. There are 

 nine or ten of them between each 

 pair of legs. They pass along the 

 ventral wall of the body, perforat- 

 ing the ventral mass of longitu- 

 dinal muscles. On their way they 

 give off nerves which innervate 

 the skin. Posteriorly the two 

 nerve-cords nearly meet immedi- 

 ately in front of the generative 

 aperture, and then, bending up- 

 wards, fall into each other dorsal 

 to the rectum. They give off a 

 series of nerves from their outer 

 borders, which present through- 

 out the trunk a fairly regular 

 arrangement. From each gan- 

 glion two large nerves (pn) are 

 given off, which, diverging some- 

 what from each other, pass into 

 the legs. 



From the oesophageal commissures, close to their junction 

 with the supra-oesophageal ganglia, a nerve arises on each side 

 which passes to the jaws, and a little in front of this, apparently 



FIG. 339.~Brain aud anterior part of 

 the ventral nerve-cords of Peripattis 

 capensis enlarged and viewed from the 

 ventral surface (after Balfour). The 

 paired appendages (d) of the ventral 

 surface of the brain are seen, and the 

 pair of sympathetic nerves (sy) arising 

 from the ventral surface of the hinder 

 part. From the commencement of 

 the oesophagual commissures pass off 

 on each side a pair of nerves to the 

 jaws (Jn). The three anterior com- 

 missures between the ventral nerve- 

 cords are placed close together ; im- 

 mediately behind them the nerve- 

 cords are swollen, to form the gangli- 

 onic enlargements from which pass off 

 to the oral papillae a pair of large 

 nerves on each side (orn). Behind 

 this the cords present a series of en- 

 largements, one pair for each pair of 

 legs, from which a pair of large nerves 

 pass off on each side to the legs (pn). 

 atn Antennary nerves ; co commissures 

 between ventral cords ; d ventral 

 appendages of brain : E eye ; en 

 nerves passing outwards from ventral 

 cord : F.q.1 ganglionic enlargements 

 from which nerves to legs pass off ; 

 jn nerves to jaws : org ganglionic en- 

 largement from which nerves to oral 

 papillae pass off : orn nerves to oral 

 papillae ; pc posterior lobe of brain ; 

 pn nerves to legs ; sy sympathetic 

 nerves. 



