378 Introduction to Animal Morphology. 



antennary nerves. The ganglia of the post-oral head 

 segments unite into a hypopharyngeal ganglion in 

 front of the ventral cord. In lulus the ventral ganglia 

 are confluent, so the entire cord has a coating of gan- 

 glion cells. A visceral nerve from the epipharyngeal 

 ganglion unites with its fellow on the oesophagus^ 

 forming a ganglion, from which an azygous branch 

 passes backwards, forming visceral ganglia, commu- 

 nicating with lateral oesophageal branches from the 

 brain ganglion also. Other visceral twigs arise from 

 the ventral ganglia. A delicate peritoneal layer, con- 

 taining transverse muscular bands, keeps the ventral 

 cord in its place, and in the fatty, concretion-holding 

 body, at each side of it, is a longitudinal blood sinus. 

 In Polydesmus, branches seem to arise from the com- 

 missures. There are no otocysts. The eyes may be 

 compound, with a facetted cornea (Scutigera), or 

 simple, in one or two rows, or in a cluster on the 

 upper or lateral part of the head ; rarely absent. The 

 optic nerve has a special ganglion. 



The oesophagus is narrow, with one pair of simple 

 (lulus), lobed (Lithobius), or three pair of grape-like 

 salivary glands (Scolopendra) ; the stomach is cylindri- 

 cal : the intestine straight, often dilated, or convoluted 

 (Glomeris), with a posterior anus ; the gastric gland- 

 cells may be hepatic, as there is no other liver ; the 

 urinary tubes are tortuous, thread-like, two (lulus) or 

 four (Scolopendra), like those of insect-larvae, opening 

 into the rectum. 



The heart is long, with a chamber for each seg- 

 ment,* separated from its fellows by valves, and with 



* Not always. In lulus, although this was the embryonic condition^ 

 they unite in pairs, so each chamber giving off two pair of branches, in 

 each segment. 



