Introduction to Animal Morphology. 2 1 1 



secrete the tube in which the worm lives. The mucous 

 glands of the clitellum in earthworms secrete a chitinous 

 material, like that of the cocoon glands of leeches. The 

 sub-dermal layer may be nucleated protoplasm (Chaetonotus), 

 simple, parallel, non-nucleated fibres, unstriped or striped, 

 longitudinal and circular ; sometimes each fibre has a cortical 

 and a medullary layer (Nephthys). The longitudinal fibres 

 arc divided into tracts by dorsal, ventral, and lateral lines. 

 Oblique fibres cross from the neuropodia to the notopodia. 

 Divp processes of this layer form septa, dividing the body 

 cavity into metameric chambers, except at the front end, 

 where the first few segments have no partitions. In Polyoph- 

 thalmus, two longitudinal septa, below and free from the di- 

 gestive tube, attached to the medio-ventral and lateral lines, 

 cut off two long chambers from the general body cavity. 

 Direct openings into the body cavity exist in Lumbricus and 

 Knchytraeus. 



The mouth opens on the peristome, and may have 

 a protrusible, cylindrical, club-like or leaf-like epi- 

 pharynx or proboscis, with a boring spine in some 

 Syllidae. The mouth may have 1-5 toothed jaws, 

 often with hooks at the base, and the peristome may 

 papillae or tubercles. The oesophagus has some- 

 times simple salivary glands, and may dilate into a 

 muscular proventriculus, in which may be chitinous 

 teeth (Gnathosyllis) and glands. The digestive canal 

 'livided into stomach and intestine, coiled in 

 Chlonema and Pherusia. It often has lateral caeca in 

 each metamere, simple or branched, with terminal 

 glandular pouches (Aphrodite). The int^line h. 



. <-pithelial, basement, and muscular coats 



triped in I'hn-oryctes). Tin- 



middl- tract of tli<- intestine may have a lining of 



itic n-iis, but has 11. arate 



gland-. In th<- iiid o-lls containing 



