180 FLOEENOE BUCHANAN. 



Here and there in the epidermis, and occupying its whole 

 thickness, are a few large coarsely granular cells with well- 

 marked large nuclei and nucleoli, probably opening to the ex- 

 terior, and secreting the material by which the animal holds 

 the fragments together which compose its temporary tube. 

 (2) The circular muscular layer (c. m.) is only very slightly 

 developed, and can scarcely be seen except in longitudinal 

 sections. It is best developed in the ventral region just 

 over the nerve-cord (where there are no longitudinal ones), 

 and can there be seen in transverse sections. (3) The 

 longitudinal muscular layer, on the other hand, is very well 

 developed, running in three bands, one dorsal and two ventral 

 (figs. 5, 6, 7, and 8, d. I. m. and v. I. m.). Although a single band, 

 the dorsal one is much more feebly developed in the median 

 line than on either side. (4) Below this again is a delicate 

 layer of coelomic epithelium, forming the outer wall of coelom, 

 and only to be distinguished by a few nuclei scattered here 

 and there on the extremities of the muscle-fibres (figs. 5, 6, 7, 

 and 8, c. ep.). 



Coming from and dividing the dorsal longitudinal muscles 

 on either side, and stretching vertically downwards to be 

 attached close to the thickened portion of the epidermis of 

 the ventral surface on either side, are, in the anterior region 

 of the body, i. e. from the 2nd to the 6th segments, very 

 distinct dorso-ventral muscles (fig. 5, c?. ^5. m.), dividing 

 the cavity of each of these segments more or less completely 

 into three longitudinal chambers. 



Besides these there are in every segment muscles going 

 from the ventral epidermic thickening on each side to the two 

 setal sacs {s. s.77i.), but these appear to be rather continuations 

 of the circular than of the longitudinal layer. Both these and 

 the dorso-ventral muscles are covered by a delicate layer of 

 coelomic epithelium. 



Alimentary Canal. — The mouth is not terminal, but is 

 overlapped by the prostomium (fig. 1, w.). The two ''cephalic" 

 tentacles, as already mentioned, arise just above it on either 

 side. The pharynx extends through the first two segments 



