No. I.] THE METAMERISM OF NEPHELIS. 47 



such until it passes the collar, when it divides into a ventral 

 and dorsal branch, and at this point of separation, as in VI, 

 lies a " Leydig's cell" (PL VII, Fig. 16). Two pairs of lateral 

 capsules lie well separated from the others, just anterior to 

 those belonging to VI, and two more, 5.5., of the ventral series 

 furnish the elements of this neuromere, V. The next nerve, IV, 

 arises as a single trunk, proceeds for a much longer distance 

 as a single trunk, sending off to the 5th annulus a dorsal branch 

 which quickly divides (PI. V). This annulus is a very narrow 

 ring lying in the plane of flexion of the oral sucker and the 

 body. The " Leydig's cell " of this neuromere lies completely 

 outside of the nerve trunk, just as it does in XXVIII or the 

 4th anal neuromere, and sends one fiber forward and one 

 backward (PL VII, Fig. 16). The two pairs of lateral capsules 

 belonging to the neuromere lie just anterior to those of neuro- 

 mere V close to the angle made by the collar. The third cap- 

 sule of the cluster at this point, lying close to, and anterior to, 

 these two, belongs to the next neuromere. III (PL VI, Figs. 1 1 

 and 13). These two lateral pairs of capsules, together with 

 two, 4.4., of the ventral capsules, complete the elements of 

 neuromere IV. The next nerve, III, arises just anterior to 

 IV and proceeds in much the same manner, dividing near 

 annulus 5 into dorsal and ventral branches. The " Leydig's 

 cell " lies alongside the trunk, as in IV (PL VII, Fig. 16). The 

 lateral capsules belonging to this neuromere show the same 

 peculiarity that Whitman found in Clepsine and that I have 

 seen in Macrobdella, — one pair lying close to the capsules 

 belonging to neuromere IV, while the other pair lies close to 

 the capsules of II, being separated by a wide space. The two 

 ventral capsules, 3.3., complete the elements of this neuromere 

 (PL VI, Figs. II and 13). 



The next nerve trunk arises from the collar as a single large 

 trunk and proceeds some little distance before it shows evidence 

 of separation, and just after separating a "Leydig's cell " appears 

 on each trunk as in III and IV (PL VII, Fig. 16). We have 

 here, then, nerves II and I as their distribution also shows. 

 The lateral capsules of II are situated on the posterior side of 

 the collar, while the most anterior, 2.2., of the ventral capsules 



