62 



OLIGOCHAETA 



a diverticulum of the oesophagus ; round the epithelium, which is columnar, is a layer 

 of tissue in which no cell boundaries could be detected ; abundant nuclei scattered 

 throughout it appear to show that it is a mass of cells ; these cells are filled with oval 

 or round particles like those which occur in the peritoneal cells in many parts of the 

 body, particularly upon the nephridia. This mass of tissue is not separated from the 

 epithelium by any membrane of any kind ; the epithelium rests directly upon it ; it 

 is traversed in various directions by blood-vessels ; towards the blind end of the pouch 

 this layer gets thinner ; at this end the lumen of the gland becomes intra-cellular ; the 



periphery of the gland in fact is 

 Fig. 15. formed of a network of tubules 



exactly like nephridial tubes, but 

 they are not ciliated, so far as 

 I have been able to discover. It 

 is a question as to whether the 

 mass of cells covering the lining 

 epithelium is peritoneal or is 

 a specialization of the lining epi- 

 thelium ; I believe the latter 

 interpretation to be the right one ; 

 as to the peripheral network of 

 fine tubes I recur to the matter 

 later. These glands or gland — for 

 they may be paired or unpaired — 

 are very diflferent in many points 

 from the calciferous glands of 

 earth-worms or from the pouches 

 appended to the gut in the Enchytraeidae. They are perhaps best to be compared 

 with a series of structures which characterise certain Eudrilidae. 



In the systematic part of this work I divide the Eudrilidae into two groups, in one 

 of which there are calciferous glands and three unpaired pouches of the same structure ; 

 in the remaining set the place of these is taken by a greater number of paired 

 bodies, closely applied to the oesophagus. These glands were first described by myself 

 in the genus Eudrlloides ; they have also been found in Stuhlmannia and a few 

 other genera. They consist of a mass of tissue exactly like that which surrounds 

 the lining epithelium of the pouch in Gordiodnlus ; this mass of tissue likewise 

 surrounds a lumen which opens into the oesophagus (in Eudnloides at any rate) ; 

 this lumen, however, is of very limited extent ; it does not nearly traverse the whole 



GOEDIODEILUS. CALCIPEEOUS GLAND. 



I. Lumen, 2. Nephriditun apparently in connexion with gland, 

 3, 4, Septa, The blood-vessels and the vascular plexuses are shadeA, 



