642 FRESH-WATER BIOLOGY 



^^ (32) Atrium and penis combined, much shorter than the remainder of 

 the sperm-duct Tubifex Lamarck 1816. 



■^\\ v\i ^\ ^\ Several species have been described from North America. 



^ -^^^''^^JL^L^L^ T. tubifex (Muller) is a widely distributed species and 



^^^> — \ ■- ^ \: " " "- abundant both in Europe and the United States. An- 



^^ t_ ^ J' ^--^"z -ijji, other species, T. multisetosus (Frank Smith) from Illinois 



'^^^-^jM^M^W' ^^ ^^^ ^^^^^ integumental papillae and conspicuous clusters 



^"' •^^^nn'^*Pp*?5p^;i^5-4^; ^j capilliform setae (Smith, 1900). (Figs. 991 and 992.) 



Fig. 992. Anterior somites oi Tubijex multisetosus. X i3- (Original.) 



34 (25. 35) Ordinarily with more than two setae in each of some or all the 



bundles; setae simple-pointed and usually nearly straight; 

 clitellum on XII and on more or less of adjacent somites; 

 Spores ordinarily on XII; spermathecal pores on IV/V. 

 Ordinarily whitish in appearance and seldom more than 

 25 mm. in length. Both terrestrial and aquatic species 

 abound Family Enchytraeidae . . 35 



There are numerous species of this family represented in the fresh waters of North America, 

 which have only recently received attention from the systematists of the group. Eisen 

 (1905) has described several fresh-water species from the Pacific Coast states belonging 

 to Mesenchytraeiis Eisen, Enchytraeus Henle and Lumbricillus Oersted. Smith and Welch 

 (1913) have described Marionina forbesae from Illinois and Welch (1914) has described 

 Luynbricillus rutilus from IlUnois. 



35 (25. 34) Ordinarily with not more than two well-developed setae per bundle, 



or eight more or less separated setae per somite. ... 36 



36 (37.42) Setae simple-pointed; J pores, 2 pairs on XI and XII or both 



pairs on XII; spermaries in X and XL 



Family Haplotaxidae. 



Haplotaxis (Phreoryctes) emissarius (Forbes) is the only representative of this family thus far 

 known in North America. Has two large isolated ventral setae and two small dorsal setae 

 oer somite; many somites without dorsal setae; length 150-200 mm.; diameter, scarcely i mm.; 

 subterranean habit. 



37 (36, 42) Setae either simple-pointed or cleft; S pores on one or more somites 



anterior to XII, with spermiducal funnels in same somites; 

 cecal diverticula of the dorsal vessel or its branches, in the 

 mid-body region Family Lumbriculidae . . 38 



38 (39) Setae cleft at distal extremities; prostomium without distinct pro- 



boscis; spermathecae and spermathecal pores paired or 

 asymmetrical in three or more somites posterior to somite 

 bearing ^ pores Lumbricillus Grube 1844. 



L. inconstans (Frank Smith), common in the Mississippi Valley, has Z pores on X or XI and 

 spermathecae in XI-XV or XII-XVI (Smith, 1905) 



39 (38) Setae simple-pointed; spermathecal pores on but one somite ante- 



rior to $ pores 40 



40 (41) Large median spermathecal sac with numerous tubular diverticula 



in VIII; with single median external opening. 



Siitroa Eisen 1888. 



Two species. 5. rostrata Eisen and 5. alpestris Eisen, each with distinct proboscis, are 

 found west of the Rocky Mountains. 



