TWO AQUATIC OiIGOCH.asTES. 



■^ lL " 



c — 

 hp - 

 cm 



lm - 



ys 



Fig. 3. 

 L. gotoi. Cross section through a fully grown setigerous organ of left dorsal side. x470. 

 c — cuticular layer, hp — hypodermis, cm— circular muscle layer, lm — longitudinal muscle layer, 

 pt — peritoneum, mf — parieto-vaginal muscle fibres, tm — interfollicular muscle, ys — young setae, 

 s — setae, ss — setigerous follicle, nys — nuclei of young follicle cells, nss — nuclei of setigerous 

 follicle. 



gradually move outwards with the completion of succeeding setae, 

 so that the organ becomes flattened antero-posteriorly and is 

 spread out sidewise. The arrangement of the setae in an organ 

 is like that of the sticks of an open fan. In the seta-forming 

 portion of the organ the cell-boundaries are also invisible, and 

 large round nucleolated nuclei are found scattered in it. 



In fully formed setigerous organs there are two sets of 

 muscles — the parieto -vaginal and the interfollicular, by which the 

 seta-bundles are moved similarly as in other oligochaetes. 



3. Aliment ae y canal. 



The alimentary canal of L. gotoi consists of four parts as in 

 other tubificid oligochsetes. They are the mouth and buccal cavity, 

 pharynx, oesophagus, and intestine. 



