378 



THE AMERICAN NATURALIST 



[Vol. XLII 



Blanchard lists in this genus the following species : 



1. 8. plicdtUis Ehrenberg 1833, from stagnant water. 



2. 8. buccalis Colin 1875, from the buccal cavity. 



3. S. obermeieri Colin 1875, from the blood of man in 

 cases of relapsing fever. The possible varieties of this 

 species, found in various types of relapsing fever, are 

 also noted. 



4. 8. dent i inn Koch 1S77, very small species from the 

 mouth. 



5. 8. gigantea Warming 1875, from brackish water. 



6. 8. eberthi (Kent 1880), from the intestine of birds. 



7. S. balbianii (Certes 1882), from the intestine of 

 lamellibranchs. 



8. 8. anserina Sakharov 1891, cause of septicemia in 

 birds. 



9. S. theUeri (Laveran 1903), from blood of cattle. 



10. S. pyogenes (Mezincescu 1904), from pus in a case 

 of pyelitis. 



11. S. gaUinarum K. Blanchard 1905, cause of septi- 

 cemia among chickens. 



12. 8. refringens Schaudinn 1905, from lesions of 

 syphilis. 



13. 8. pertenuis Castellani 1905, from lesions of yaws. 



14. 8. ovina R. Blanchard 1906, from blood of sheep. 



15. 8. vincenti R. Blanchard 1906, from abscesses in 

 man. 



Also several other uncertain forms. 



It is evident that this assemblage of forms is not 

 entirely natural. Of many little is known beyond the 

 size and manner of life. The latter presents radical dif- 

 ferences, but the formation of new genera on purely physi- 

 ological grounds is recognized as a most dangerous pro- 

 cedure. No doubt better knowledge, especially of the life 

 cycles, will lead to the removal of groups of these species 

 to new genera, but such must be based upon distinctive 

 characteristics; any other method only results in greater 

 confusion. New forms are being described constantly, 

 e. g., S. lymphatica, which "White and Proescher regard 



