NERVOUS SYSTEM. 



557 



placed in the lateral compartments 

 of the body-cavity immediately 

 dorsal to the ventral nerve cords 

 and extend backwards for a very 

 variable distance in the different 

 species (Fig. 33S, s.g), sometimes 

 for not more than half the length 

 of the body and sometimes for 

 nearly its whole length. Immedi- 

 ately behind the mouth and in 

 front of the first pair of legs they 

 bend inwards and ventralwards 

 and fall, one on each side, into 

 the narrow hind end of the buccal 

 cavity. They consist of an un- 

 branched tube on each side, the 

 lining of which is the glandular 

 tissue of the gland and the front 

 end of which receives the opening 

 of a vesicle with vacuolated pro- 

 toplasmic wall. The salivary glands 

 are the nephridia of the segment 

 of the oral papillae and the just- 

 mentioned vesicles are their end- 

 sacs. 



The central nervous system con- 

 sists of a pair of supra-oeso- 

 phageal ganglia united in the 

 middle line, and of a pair of widely 

 divaricated ventral cords, con- 

 tinuous in front with the supra- 

 oesophageal ganglia (Fig. 339). 



The ventral cords at first sight 

 appear to be without ganglionic 

 thickenings, but on more careful 

 examination they are found to be 

 enlarged at the level of each pair of 

 legs (Fig. 339). These enlargements 

 may be regarded as imperfect gan- 

 glia. There are, therefore, as many 



n 



A.. 



FIG. 338. Peripatus capensis dissected 

 so as to show the alimentary canal, 

 slime glands, and salivary glands (after 

 Balfour). The dissection is viewed 

 from the ventral side, and the lips (L) 

 have been cut through in the middle 

 line behind and pulled outwards so 

 as to expose the jaws (;'), which have 

 been turned outwards, and the tongue 

 (T) bearing a median 'row of chitinous 

 teeth, which branches behind into 

 two. The muscular pharynx, extend- 

 ing back into the space between the 

 first and second pairs of legs, is fol- 

 lowed by a short tubular oesophagus. 

 The latter opens into the large stomach 

 with plicated walls, extending almost 

 to the hind end of the animal. The 

 stomach at its point of junction with 

 the rectum presents an S-shaped ven- 

 tro-dorsal curve. A anus ; at an- 

 tenna ; F.I, F.2 first and second legs ; 

 j jaws ; L lips ; oe oesophagus ; or.f 

 oral papilla ; ph pharynx : R rectum ; 

 s.d salivary duct : s.g salivary gland : 

 sl.d slime reservoir ; sl.g portion of 

 tubules of slime gland; st stomach- 

 T, tongue in roof of mouth. 



