ANNELIDA 



79 



presents the following regions in succession. The mouth 

 opens into a buccal cavity which is protrusible, formed of 

 folds and cavities, and suspended by strands of muscle from 

 the forward region of the body wall which are directed 

 forwards to be inserted into it. The pharynx succeeds as 

 a bulbous region. It is strongly folded on its dorsal side, 

 and its thickness is due to the great development of musQle 

 on its upper side, and it is also supported to the body wall 

 by muscle strands. The oesophagus extends from the pharynx 

 to the thirteenth segment. In the relaxed condition it 

 presents a series of constrictions where the septa encircle it. 



Cer. gang. Dors. ves. Heart Dors, pore 



2 



Typltlosole 



Mouth I Pfiar. 

 Buc. cav. 



Vent. Sub- Oes. \ Oes. glds. Crop 

 ves. neur. Nerve 

 ves. cord 



Gizzard 



Int. 



FIG. 37. Lumbricus terrestris. General view of the organisation 

 of the anterior end. 



The three pairs of oesophageal glands are swellings of the tube 

 in segments 10, 11, and 12. The first pair open widely into the 

 oesophagus. The others are folded into a series of passages 

 and secrete a milky fluid which is discharged by a duct on 

 each side into the oesophagus, just in front of the crop. These 

 glands may be easily distinguished, besides, by the opaque 

 white lime they contain. The crop is a distension of the tube 

 behind the oesophagus, and it extends to the interval between 

 the fifteenth and sixteenth, when it gives place to the muscular 

 gizzard, and this extends to the end of the nineteenth segment. 

 The intestine leads from the gizzard to the anus, and the tube 

 is similar throughout : it presents a series of slight swellings 

 and constrictions opposite the segments and septa, and the 

 dorsal wall is folded inwards, forming a longitudinal ridge 

 projecting into the lumen. This fold is called the typhlosole. 

 The walls of the intestine', including the typhlosole, are folded, 



