430 mVERTEBBATE MORPHOLOQT. 



bounded behind by a pair of processes whicb represent a 

 lower lip and are known as the chilaria (Fig. 195, chi). The 

 oesophagus passes upwards and forwards and dilates into a 

 large proventriculus (Fig. 196, pr) in the front part of the 

 cephalothoracic shield, and this, bending upon itself and 

 constricting again, opens into the stomach (s), from which the 

 intestine (i) passes straight back to open on the ventral sur- 

 face of the body at the base of the terminal spine. The inner 

 wall of the hind-gut, oesophagus, and proventriculus is lined 

 by chitin, which in the last-named structure is thrown into 



ht 



vn 



Fig. 196. — LoNGiTtTDiisrAL Section through a young Limulus polyphemus, 



DiAGKAMMATic (after Packard). 



ce = cerebral ganglion. I = liver. 



JU = heart. pi- = proventriculus. 



i = intestine. s = stomach. 



vn = ventral nerve-cord. 



folds and recalls the masticatory apparatus in the stomach 

 of the Decapodous Crustacea. Into the stomach there open 

 the ducts of two pairs of voluminous digestive glands (?) 

 which occupy the greater portion of the cephalothorax and 

 are much branched greenish structures. 



The nervous system consists of a syncerebrum (ce) com- 

 posed apparently of three pairs of ganglia. It lies in front of 

 the oesophagus, sending branches to the compound and simple 

 eyes. Behind the oesophagus and united with the syncere- 

 brum by circumoesophageal connectives comes a series of 

 seven pairs of ganglia closely approximated, the first pair 

 innervating the chelicerse and the remaining six the other 

 thoracic limbs in succession. A chain of six pairs of ganglia 

 lying in the abdomen is connected with the cephalothoracic 

 series and innervate the abdominal appendages. 



