GENERAL SYSTEMATIC BACTERIOLOGY 227 



ent recognizable with certainty. Ehrenberg (1828, 1830, 1836), Dujar- 

 din (1841), Perty (1852), Cohn (1854), Davaine (1864), Luders (1866), 

 Davaine (1868). 



2. Cohnian conception. Short cyHndric or elliptic cells, never in 

 chains or filaments. Alternating motility and non-motility. Shape 

 and grouping the primary characteristics. No definite designation of 

 a type species, although in the earlier writings Bacterium termo is fre- 

 quently mentioned. Cohn (1872, 1875), Lister (1873), Lankester 

 (1873), DaUinger and Drysdale (1874), Magnin (1878), Winter (1879), 

 Luerssen (1879), Trevisan (1879), Grove (1884), Van Tieghem (1884), 

 Escherich (1885), Fliigge (1886). 



3. Zopfian conception. Rod shaped organisms which produce no 

 endospores. Motility and grouping of cells regarded as secondaiy or 

 non-essential characters. No type species designated. Zopf (1885), 

 Hueppe (1895), Schroeter (1886), De Toni and Trevisan (1889), Ludwig 

 (1892), Freudenreich (1894), Lehmann and Neumann (1896), Fliigge 

 (1908). Lohnis (1913). 



4. Not recognized as a generic name. Forms usually included under 

 Bacillus or other genera. Baumgarten (1890), Sternberg (1892) , Fischer 

 (1897), Matzuschita (1902), Schneider (1912), Breed, Conn and Baker 

 (1918), Castellani and Chalmers (1919), Bergey et al. (1923). 



5. Migula's conception. Non-motile, rod-shaped bacteria. No type 

 designated definitely, unless it be Bacterium anthracis (Davaine) Migula. 

 Migula (1895, 1897, 1904), Chester (1901), Smith (1902), Kendall (1902), 

 Ellis (1909), Heim (1911). 



6. Smith-Vuillemin conception. Rod-shaped organisms with polar 

 flagella, type same one of the fluorescent bacteria, such as Bacterium 

 aeruginosum (Schroeter) Cohn (Bacterium pijocyaneum (Gessard) 

 Vuillemin). E. F. Smith (1905), Vuillemin (1913). 



7. Conception of Orla- Jensen. The genus to be defined to include 

 Bacterium coli Escherich as the type. Practically the colon-typhoid 

 group. Jensen (1909), Buchanan (1918), Committee (1918-1920). 



Of the species of Bacterium named before Cohn's description in 1872, 

 there does not seem to be a single one that can be identified with cer- 

 tainty. Certain species of other genera can be recognized, but no 

 organism designated Bacterium. The diagnosis of the genus given by 

 Cohn was soon found to include forms that were diverse, and proved 

 impracticable. However, certain of the species described and recog- 

 nized by him can be identified. 



