74 BOTANICAL GAZETTE [JANUARY 
pertaining to such mutations may be recorded photographically 
(28), and the possibilities thus afforded for the study of bacterial 
mutations in certain groups, notably in that of the tetanus bacillus 
(29), are unlimited. 
The Society of American Bacteriologists (2) proposes the use of 
the botanical rules adopted at the Vienna Congress (44) in 1908 
for the purposes of bacterial classification. In many ways the 
scheme formulated during a century and a half by the botanists is 
excellent for the purpose, although in some ways we are not ready 
for it. It is composed of stems and twigs and branches. When 
we pick up a bacterial group, we do not know whether to call it 
a stem or a twig or a branch, for the leaves have mostly grown on 
trunks. The tendency has been to work downward, to call a 
superficially recognized group a species and subdivide it into types, 
and to number the types. Why not work upward, call the numbered 
types species, and have more room for classification ? 
Bacteriologists, trained in pathological laboratories, have per- 
haps laid too little emphasis on the necessity of observing the laws 
of heredity in making classifications. It seems as though an appli- 
cation of these laws, with the same scale of nomenclature used by 
the classifiers of higher plants, might well be applied to the system- 
atic arrangement of bacteria. Thus a tetanus strain of a pure 
biotype may give rise to many biotypes, as shown by colony forma- 
tion. These derivative types are all typical tetanus bacilli. They 
represent elementary species, and are too many to catalogue, being | 
of interest only to the student of heredity. They are no more 
deserving of specific names than are the commonly observed small 
mutations of higher plants and animals, and if named would require 
a trinomial nomenclature. There are some definite protein sub- 
stances, however, differing radically in various tetanus bacilli, 
that probably are not subject to active mutation and are demon- 
strable by an immune reaction, agglutination. Four groups of 
tetanus bacilli have thus been distinguished by TuLtocn (45, 46), 
and four groups of vibrion septique bacilli by RoBERTSON (42). 
In the colon-typhoid group this reaction has long been considered 
specific, why not in these? To be sure, the details of the reaction 
