76 BOTANICAL GAZETTE [JANUARY 
a bacteriologist who finds a new type that has originated in his own 
hands should not dignify it by the name of species, if he can show 
that such a change affects several characters. 
GENUS.—Organisms that show the same general reactions on 
ordinary media and have the same general morphological habit may 
be grouped in genera. Such a scheme will compel the classification 
of most of the old and well recognized anaerobic species as genera, 
although it will unite some, such as Novy’s bacillus and B. oede- 
matiens, and vibrion septique and the whale septicaemia bacillus 
into genera. It gives to the words species and genus approximately 
the same rank, in relation to mutational possibilities, as they possess 
among the higher forms. A vibrion septique strain can no more 
mutate to a sporogenes habit than can a pine tree mutate to an 
oak, but it can mutate in small detailed characters that may be of 
interest, and there are vibrion septique strains that differ in more 
fixed characters and that should be given specific differentiation. 
A detailed plan (27) following these lines has already been 
presented. It is intended as a preliminary classification. Twenty- 
seven anaerobic genera have been defined, many more will have to 
be admitted in time, especially in the proteolytic group, and when 
large collections have been studied many emendations will have to 
be made. An organization (26) of these genera has been prepared, 
employing chemical criteria only; morphological criteria are found 
entirely inadequate for purposes of classification in this group. 
It has been thought premature to group the genera into tribes. 
Two subfamilies include all the anaerobic rods described in the 
genera. 
Subfamily I. Clostridioideae—— Clostridiaceae that on meat 
medium produce after twenty days’ incubation under oil at 37° 
a reaction of P, 7.0 or a more acid reaction, the culture having 
been boiled after incubation. Type genus Rivoltillus, the vibrion 
septique type as described by HELLER (25). 
Subfamily II. Putrificoideae.—Clostridiaceae that on meat 
medium produce after twenty days’ incubation at 37° under oil a 
reaction of P, 7.1 or a more alkaline reaction, the culture having 
been boiled after incubation. Type genus Metchnikovillus, the 
sporogenes type as defined in the description of Bacillus sporogenes, 
