MORPHOLOGY OF MELIBE 557 



together in such ii way that under a low magnification they 

 appear to form tufts which give to the Hning the appearance 

 of flask-shaped cells (PL 35, figs. 61, 64). Higher magnification 

 brings out their true nature, that they are moderately columnar 

 cells with large cilia nearly four times longer than the cell (PI. 36, 

 figs. 67, 68, 69). The renal syrinx communicates with the 

 pericardium by a cyncitial plate with the nuclei scattered, 

 but as a rule nearer the base, i. e . toward the syringeal 

 side (figs. 66, 67, Sypl). It communicates with the ureter, 

 however, by a rather wide opening (fig. 61). There is 

 then no reno -pericardial pore between the kidney and peri- 

 cardium, through the renal syrinx. This I have determined 

 by the study of serial sections of the organ. E 1 y s i a , according 

 to Lankester (1906 : 110), is exceptional in that the kidney is 

 placed below and partly surrounds the pericardium, and the 

 reno-pericardial orifices are multiple, some ten being present. 

 And, according to Shipley and MacBride (1915) there is a reno- 

 pericardial canal, a narrow ciliated passage, between the 

 kidney and pericardium in the molluscs. In Melibe leonina 

 on the pericardial side, the renal syrinx narrows into a neck 

 (PI. 35, fig. 60, P), which internally is formed into two channels 

 by a plica or villus which extends from the cyncitial plate and 

 into the organ (PI. 35, figs. 64, 65, PI. 36. fig, 67, PJ). Only about 

 one-third of this villus is ciliated, that is, its tip, or the part 

 farthest away from the cyncitial plate. The sides of the syrinx 

 opposite the non-ciliated portion of the villus are also non- 

 ciliated. The non-ciliated part of the walls has a large number of 

 nuclei situated near the surface. The structure of the ciliated 

 columnar cells of the renal syrinx, or pyriform organ, in 

 M. leonina, shows the same remarkable feature as in the 

 intestine, viz. the individuality of the cilia as they pass into 

 the cell. In the renal syrinx there is first the plainly visible 

 terminal bars, but unlike the condition found in the intestine, 

 the terminal bars (basal granules) are shown only as one row, 

 or one for each cilium. From the terminal bar the cilium con- 

 tinues to the base of the cell as a distinctly granular fibrillar 

 structure. As in the intestine (PI. 33, fig. 45, Bm), the basement 



