336 MOORE. [Vol. XIII. 



instabilia scarcely more than its ciliated mouth appears. The 

 second funnel has the same relation to its nephridium as the 

 first, but owing to its reversed position hangs from the anterior 

 ventral margin and faces forward. Fig. ii, which represents a 

 horizontal section near the floor of the body of B. instabilia, 

 shows the relation of the pre-genital funnels to the coelom. 

 The first one {t!) lies entirely within somite II, but very close 

 to its posterior septum, where it is held by the efferent duct 

 which perforates that septum. The second funnel (/") is 

 similarly held by its efferent duct close to the point where that 

 duct enters the body-wall of somite III. In B. illuminatus the 

 imperfect septa permit a greater range of movement to the fun- 

 nels, and the anterior one is frequently found in somite III, 

 which it always faces. Figs. 13, 14, and 15 show respectively 

 the points where the funnels enter the plexuses of B. illumi- 

 natus, B. pulcherrima, and B. philadelphicus, all on the extreme 

 ventral margins {tp, t, and/i"). Fig. i also shows its relation 

 to the plexus. The funnels of the posterior nephridia lie in 

 lateral positions about the middle of somite VIII, and face pos- 

 teriorly and mesially. Their relation to the plexus is the same 

 as in the anterior nephridia (PI. XXI, Fig. 12, t). 



The funnels of the several species, although agreeing in 

 essential structure, differ somewhat in form. That of Bdello- 

 drilus illuminatus (PI, XXI, Figs. 5, 6, 7) has somewhat the 

 shape of a leg of mutton, its stalk being somewhat narrowed 

 and constricted by the enclosing folds of the efferent tubule, 

 the free portion decidedly enlarged and the nephrostomal end 

 oblique and somewhat constricted. In B. philadelphicus (Fig. 

 8) the funnel is more or less irregularly pear-shaped, but also 

 slightly flattened, oblique, and swollen. Branchiobdella instabilia 

 and pulcherrima have very pretty symmetrical funnels of nearly 

 the bell-jar shape described for B. parasita by Dorner, but here 

 also somewhat flattened (Fig. 9). The nephrostomata also 

 differ; that of B. illuminatus is small and elliptical, or sometimes 

 slit-like, that of B. instabilia larger and rounded, and that of 

 B. philadelphicus very conspicuous, and in the example figured 

 (Fig. 8) as large as the funnel cavity, which is much wider than 

 the nephrostome in B. illuminatus (Fig. 5). 



