318 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



narrower than, the gland cells. The nuclei of these cells 

 are oval in shape, and may be situated in any part of the 

 cell (fig. 12, in. c). Certain fibres from the longitudinal 

 muscular layer may turn outwards and come into close 

 contact with the inner ends of the gland cells. 



3. The Circular Muscle Layer lies just within the 

 epidermis. It is an extremely delicate layer, and is with 

 difficulty recognised in transverse and longitudinal 

 sections. Occasionally it can be fairly clearly seen in an 

 oblique section, when the individual fibres appear as 

 incomplete bands surrounding the body (fig. 5, c. m.). 



4. The Longitudinal Muscles are better developed 

 than the circular, and can be seen in longitudinal 

 sections of the body wall as elongate fibres. Seen in 

 transverse section they have the appearance of flat plates 

 or lamellae embedded in a granular substance. There is 

 no axial core, as is so characteristic of the longitudinal 

 muscles of Lumbricus, neither are they divided into 

 dorsal and ventral regions by lateral lines, as is described 

 by Nomura (1913) for Limnodrilus gotoi (fig. 5, I. to.). 



5. The Peritoneal Epithelium consists of a single 

 layer of somewhat flattened cells with prominent rounded 

 nuclei. 



COELOM AND COELOMIC FLUID. 



The coelom of Tubifex rivulorum is, as is usual in 

 the Oligochaeta, well marked and spacious, and divided 

 into a series of compartments by septa. The number and 

 arrangement of the septa correspond to the external 

 segmentation of the body. The septa between segments 

 1 to 4 are incomplete. The coelom only communicates 

 indirectly with the exterior — by means of the nephridia 

 and genital ducts. There are no dorsal pores such as are 



