510 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



ALIMENTARY CANAL (PI. III). 



As usual in the Arthropoda, three regions of the 

 alimentary canal may be recognised. The fore-gut or 

 stomodaeum — comprising the oesophagus and stomach — 

 which is lined with cuticle ; the mid-gut or mesenteron, 

 which is soft-walled and has no chitinous lining ; and 

 the hind-gut or proctodaeum — a term synonymous with 

 rectum in this animal — which is also lined with a 

 chitinous cuticle. 



Fore-Gut. 



The Mouth is a laterally ovate aperture lying behind 

 the foot jaws. It is directly covered by the pair of 

 mandibles. In front of the opening — which is directed 

 downwards — is a broad tripartite fleshy lobe, the labrurn, 

 and behind it is a smaller lip, the metastoma. The 

 mouth leads directly into the Oesophagus, a thick-walled 

 tube whose lumen is greatly constricted by three 

 massive infoldings of the wall (fig. 20). Bright red 

 pigment is always contained in the walls of the 

 oesophagus. Three bunches of stellate glands — two 

 antero-lateral and one posterior — are present at its 

 proximal end, and similar glands are scattered in the lips 

 of the mouth. Each' gland is globular, and the somewhat 

 conical cells composing it are»radially placed round a 

 small central cavity. From the cavity a narrow duct, 

 which is almost certainly a single cell, leads to the 

 surface. Similar glands occur in large masses in the 

 walls of the rectum. There seems no reason why these 

 glands should have any other function than that of 

 lubricating the walls of the passages in which they are 

 found, in order to facilitate the ingress and expulsion 

 of the food matter. It is difficult to conceive of anv 



