638 



FRESH-WATER BIOLOGY 



KEY TO NORTH AMERICAN FRESH-WATER OLIGOCHAETA 



1 (45) Well-developed setae present on most somites 2 



2 (24) Reproduction chiefly asexual, by budding; sexual reproduction 



less frequent. Clitellum, when present, on some somites of 

 V-VIII. Length less than 25 mm. in most species. . 3 



3 (4) Setae of ventral bundles as well as dorsal setae capilliform; septa 



imperfectly developed; prostomium broad and ciliated ven- 

 trally; integument of most species contains conspicuous 

 colored bodies of some shade of red, green, or yellow. Usu- 

 ally 1-2 nmi. long Family Aeolosomatidae. 



A eolosoma Ehrenberg is the only North American 

 genus and the species of the U. S. have not been 

 much studied. A . tenehrarum Vejdovsky has pale 

 yellow or greenish integumental bodies. One or 

 two species with colorless bodies are known. A. 

 hemprichi Ehrenberg has salmon-colored bodies. 

 This last named species thrives exceptionally well 

 in hay infusions and in similar cultures from wheat 

 and thus large numbers are readily obtained for 

 experimental purposes. 



Fig. 981. Aeolosoma hemprichi. 

 Lankester.) 



X 20. (After 



4(3) 



Ventral setae all uncinate (Fig. 991); septa well developed; no 

 brightly colored integumental bodies. 



Family Naididae . . 5 



5 (8) No dorsal setae 6 



6 (7) Ventral bundles of setae on III-V as on other somites. 



Schmardaella Michaelsen 1900. 

 The South American species 5. filiformis (Schmarda) has recently been reported from Lake 

 St. Clair (Moore, 1906). 



7 (6) No setae on III-V. Somite III much elongated. 



Chaetogaster K. von Baer 1827. 



Several species are known 

 from North America, of which 

 C. limnaei K. von Baer, which 

 lives in mollusks, and the large 

 transparent C. diaphanus 

 (Gruithuisen), 10-15 mm. long, 

 are easily recognized. 



Chaetogaster limnaei. X 40. 

 (After Lankester.) 



8 (5) Setae in both dorsal and ventral bundles 9 



0(12) No capilliform setae in dorsal bimdles. .......... ip 



