772 CONTRIBUTION TO AUSTRALASIAN OLIGOCH^TA, I., 



Digestive system. — The pharynx is a thick-walled chamber 

 extending from the buccal cavity in the first segment to the 

 posterior region of the fourth segment. It is somewhat com- 

 pressed laterally, and the antero-dorsal portion of its cavity is 

 produced into a pocket which is sent off anteriorly and obliquely 

 towards the dorsal surface. The formation of this pouch is due 

 to the presence, in the middle of the anterior boundary of the 

 pharynx, of a mass containing an abundance of nerve-cells which 

 become continuous with the posterior portion of the brain. 

 Judging from its constitution one would be inclined to regard 

 this structure as a sensory or tasting organ. The wall of the 

 pharynx consists of very tall columnar cells provided with very 

 long cilia. External to this epithelium is a layer of longitudinal 

 muscle-fibres connected with the body-wall above and below, and 

 with the prostomium. 



The oesophagus extends from segments iv.-xiv., in the form of 

 a sinuous tube whose contour shows only a very slight constric- 

 tion in the region of the septa. On entering segment xi., it 

 becomes displaced from the central position which it has occupied 

 so far in the body, towards the ventral body-wall owing to the 

 great mass of developing spermatozoa which are present in that 

 segment. It maintains this position throughout its further 

 extent, and, in segment xiv., rises to a more central position in 

 the body-cavity, and passes into the intestine which commences 

 in segment xv. The portion of the intestine situated in segments 

 xv.-xviii., inclusive, is constricted so as to form a well pronounced 

 pouch in each of those segments. Behind this, the pouches 

 become less and less distinct. The intestine contains an abundance 

 of foreign material, diatom valves, etc. The digestive canal is 

 provided throughout with exceedingly long cilia. The wall of 

 the oesophagus differs from that of the intestine in being much 

 folded, and in having an epithelium of slightly taller cells. The 

 iutestine has its wall covered by a plexus of bloodvessels, and 

 this no doubt is connected with the digestive function. 



Vascular system. — The attempt to make an entire reconstruc- 

 tion of the blood-vascular system is attended with great difficul- 



