ANNELIDA. 57. 



which they hold in place. Fore-gut (buccal pouch, pharynx), 

 mid-gut (gullet, crop, gizzard, intestine), and hind-gut (rectum) 

 are distinguishable. 



The mouth, for which the prostomium and peristomium form 

 upper and lower lips, leads into a small, thick-walled eversible 

 buccal pouch (b.p). This is connected by muscle-fibres with the 

 wall of the body in front of it. The walls of the mouth-cavity 

 contained in the pouch are raised into numerous folds. Next 

 follows the oval pharynx (ph) which is placed in segments 3-6. 

 It is very thick- walled, and connected by numerous retractor 

 muscle -fibres with the body- wall. The posterior end of the 

 pharynx is continued into the tubular gullet or cesophagus (ce) 

 which occupies segments 7-14, and bulges out slightly in each 

 of them. Three pairs of swellings (ce.gl) are to be seen on the 

 sides of the gullet in segments 10, 11, and 12 respectively. The 

 anterior pair (oesophageal pouches) are outgrowths from the 

 gullet, while the others (oesophageal or calciferous glands) are 

 glandular thickenings in which carbonate of lime is secreted. 

 The calciferous glands contain a number of small cavities, which 

 communicate with the oesophageal pouches. In 13 to 16, the 

 oesophagus expands into a rounded chamber, the crop (cr), with 

 rather thicker walls. Behind this comes the thick-walled gizzard 

 (gz) of similar shape, extending back to about segment 1 9. The 

 rest of the alimentary canal is almost entirely formed by the 

 thin-walled intestine (i), which is dilated in each segment. Its 

 dorsal wall is pushed in, so to speak, and forms a thick, longitud- 

 inal ridge, the typhlosole, which projects into the intestinal cavity 

 from its dorsal side. Its surface is raised into transverse ridges. 

 The outside of the intestine is covered by a thin layer of yellowish- 

 brown cells (chloragogen cells), which also fill up the cavity of 

 the typhlosole, and form the so-called liver. The gut is com- 

 pleted by a very short thin-walled rectum which occupies the last 

 segment. 



The alimentary canal is lined with simple columnar epithelium, 

 the surface of which, except in the intestine, is covered by a 

 cuticle that is especially thick and firm in the gizzard. The 

 glandular cells of the calciferous glands are of epithelial nature, 

 and so are a number of small glands which open into the pharynx. 

 A sub-epithelial layer follows, composed of connective-tissue, in 

 which is a network of blood-vessels. Externally is a muscular 



