TUBIFEX. 317 



Ekitaro Nomura (1913), in his description of 

 Limnodrilus gotoi, gives a short account of the clitellar 

 gland cells as they occur in that worm. He says that the 

 gland cells are 20-23 n long, that is, four times the 

 length of the ordinary clitellar cells, and 8-10 /* across. 

 " Three well-marked stages can generally be observed in 

 mature specimens : a highly vacuolated condition, a more 

 or less granulated condition, and one in which the cells 

 contain many globules.' ' 



In most of the specimens of T. rivulorum that I 

 examined the clitellar gland cells were only a little larger 

 than the ordinary gland cells, and the contents were 

 granular. In a few cases, however, the clitellum was 

 enormously enlarged, and I can only suppose that the 

 maximum development of the clitellum is not reached 

 until a very short time previous to the forma- 

 tion of the cocoon. The cells at this time may be 

 as much as 40 /* to 45 /* long, and 11 n to 14 /x across 

 (PL III, fig. 12). They are almost oblong in shape, 

 tapering just a little at the inner end. The nuclei are 

 still visible, but are much less distinct. They remain 

 near the inner end of the cell. The increase in size of 

 the cells at this time is accompanied by the deposition in 

 them of a large number of globules of the secretion which 

 forms the cocoon. Many of the cells are quite full of the 

 secretion, which masks, almost completely, the cyto- 

 plasmic contents. In others, where the secretion is 

 present in smaller quantities, it is arranged fairly 

 regularly in the form of rounded masses, 2 fi in diameter, 

 which congregate principally near the lateral walls of the 

 cell, where they are arranged in longitudinal rows 

 (PL III, fig. 12, se. c). The cytoplasm is somewhat 

 vacuolated. Between these enlarged and modified gland 

 cells are supporting cells, which are as long as, but much 



