36 BRISTOL. [VOL. I. 



sucker is not prominent, and the anal sucker is small. The 

 male orifice lies normally between annuli 36 and 37. The 

 female orifice lies normally between annuli 38 and 39. 



The first pair of nephridiopores lies between annuli 16 and 

 17, at the posterior edge of the seventh (VII) metamere. There 

 are four pairs of nephriclia anterior to the male orifice, while 

 posterior to them are 13 pairs of pores, the last pair lying 

 between annuli 96 and 97. The nephridiopores are separated 

 by five annuli. The anus is dorsal and lies behind the iO4th 

 annulus. The clitellum consists of 15 annuli --from 28 to 42 

 inclusive. It includes the last four rings of metamere X and 

 the first of metamere XII. 



The whole number of metameres is 34. In the body region 

 they consist of five annuli each, as is shown externally by the 

 nephridiopores. In the terminal regions these are more or 

 less reduced and the limits were determined by the innervation 

 as follows : 



I consists of the prostomium ; II of annuli 2 and 3 ; III of 

 a single ring, 4; IV of a single ring, 5; V of 6, 7, 8; VI of 9, 

 10, ii. Metameres VII to XXIV, inclusive, are normal, com- 

 posed of five rings each. XXV consists of annuli 102, 103, 

 and the anterior half of 104 ; XXVI, of the posterior half of 

 104 and 105. XXVII consists of 106, the last annulus and 

 the acetabulum, the top part of the sucker. XXVIII to 

 XXXIV consist of the sucker disc. 



The number of eyes is six ; and they are arranged in pairs: 

 the first pair lies in the second annulus and looks forward ; the 

 second pair lies wholly in the fourth and looks outward and back- 

 ward; the third pair lies partly in the fourth and partly in the 

 fifth and looks outward and backward. 



Habitat. Nephelis is found in fresh-water brooks and ponds 

 wherever food is plentiful. They are not parasitic, but feed on 

 the debris of animals as does Aulastoma. They are usually 

 found partly buried in mud or sand or on the under side of 

 submerged objects. 



Nervous System. The nervous system consists of three 

 well-marked divisions: the central, the sympathetic, and the 

 intermuscular systems. 



