CERTAIN GENERA OF THE CLOSTRIDIACEAE 3 



must classifj' them as do the botanists and not as do the bacteriol- 

 ogists. The family of Orchidcae has 334 genera, the Graviineae 

 298, the Rubiaceae 377, the Leguminoseae 399, and the Compositae 

 766 (Bentham and Hooker). The following classification imi- 

 tates the taxonomic arrangement of botanical classifications in 

 preference to bacteriological. It must be borne in mind that 

 the date 1920 in bacteriologic systematics corresponds roughly 

 to the date 1760 in botanical systematics. 



Relative to the evolutionary history of the anaerobes we know 

 nothing, but conjectures are not entirely out of place. Proteins 

 and carbohydrates have existed together and have been destroyed 

 by bacterial action since a remote geologic epoch. We cannot 

 tell whether the organic catalyzers of one type of substance 

 antedated those of the other or whether they are closely related. 

 Botanists are not agreed as to what form of life first tenanted 

 the globe. When looking for ancestral forms it is natural to 

 seek in a group of organisms of great catalytic activity like the 

 Clostridiaceae, for tj^pes which may synthesize simple substances, 

 and if such are discovered it is not out of place to regard them as 

 more closely related to the hypothetical ances'tors of the group 

 than those that do not synthesize inorganic substances. Such 

 reasoning is of course entirely dependent on the homogeneity 

 of the group under discussion. We have no means of proving 

 the homogeneity of the Clostridiaceae. But when classified 

 according to their chemical activities these organisms form a 

 remarkable chain whose links we are all but warranted in regard- 

 ing as the varied end points of an evolutionary process. As 

 our most primitive type we may well choose the nitrogen-fixing 

 anaerobes of the soil. It is to Winogradsky that we turn for 

 the first demonstration of such organisms. He named his 

 anaerobic nitrogen-fixing organism Clostridium Pastorianum. 

 Bredemann declares that nitrogen-fixation is a variable power 

 among all organisms of the amylobacter type, and he includes 

 under the name amylobacter, Clostridium Pastorianum of which 

 bacillus he possesses a strain. These organisms are highly 

 saccharolj^tic, being pectin fermenters, and they do not split 

 gelatin. Farther up the scale we find anaerobic rods which 



