316 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



cytoplasm of these cells is densely granular. The nuclei 

 are rounded or slightly oval in shape, and each contains a 

 nucleolus (PI. II, fig. 5, hyp.). 



The gland cells are separated from one another by the 

 columnar epidermal cells, or "supporting cells" as 

 Atheston (1898) calls them. They are narrower than the 

 gland cells, generally columnar in outline with the 

 broader end lying next to the cuticle. The nuclei are 

 oval in shape, quite conspicuous, and situated near the 

 middle of the cell. 



(6) Clitellar Epidermis. The clitellum does not 

 develop until the worm has nearly reached sexual 

 maturity. It then becomes differentiated from the 

 ordinary epidermal cells, and is confined to the principal 

 reproductive segments, viz., segments 11 and 12. It has 

 the form of a complete girdle, but is less well developed 

 on the ventral than dorsal surface. It merges gradually 

 into the ordinary epidermis anteriorly and posteriorly. 

 It is discontinuous, of course, at the openings of the 

 setigerous follicles, the spermathecal pore and penis. 



It is composed of a single layer of cells throughout. 

 At first, the cells are little different from the ordinary 

 gland cells of the epidermis. The nucleus is a con- 

 spicuous rounded body, situated at the base of the cell, 

 and exhibits a very well-marked reticulum with a 

 nucleolus. The cytoplasmic contents of the cell are 

 finely granular. 



This is the usual structure of the clitellum, even in 

 individuals which appear to be quite mature, and, 

 consequently, this is the condition which has been 

 described by most observers. Atheston (1898), for 

 example, says of the gland cells of the clitellum that they 

 are smaller and more numerous than those of the ordinary 

 epidermis, otherwise they are similar. 



