iio Marshall Ward '. — On the Characters , or 
between the Montsouris Observatory in Paris, and the various 
German institutes of hygiene : the former severely criticises 
the gelatine-plate method as untrustworthy, the latter employ 
it almost exclusively. 
Enough has been said to show how it has come about that 
various bands of observers have been traversing and mapping 
out the enormous domain of bacteriology, each with little or 
no regard for the presence or work of the other. The result 
may be compared to a number of maps, begun by various 
parties of surveyors, each starting along a different route and 
with no pre-arranged plans as to scales, comparative surveys, 
or intercommunication of any particular kind. Moreover, one 
set of explorers has confined its attention chiefly to contours, 
while another has recorded climate, and another artistic 
features, and so on, whence the difficulties of comparing the 
results and compiling a map up to date are very great. 
All are more or less conscious of the need of a good 
systematic account of these organisms, however ; and I now 
propose to try and set forth in some detail what kinds of 
characters are being used by those who wish to inform others 
how given ‘ species ’ may be distinguished. I shall of course 
confine my remarks entirely to modern work. 
In order to remind the reader of the scheme propounded 
by Cohn, I append his system in a tabular form (Table I) as 
put forward in 1875. 
TABLE I. — Cohn, 1875. 
Tribe I. Gloeogenae. 
Cells free, or connected by intercellular substance into slimy colonies 
(zoogloeae). 
A. Cells free, or grouped in pairs or fours. 
Chroococcus (Naeg.). Cells globular. 
Synechococcus (Naeg.). Cells cylindrical. 
B. Cells, in the resting state, gathered into amorphous zoogloea- 
masses. 
(a) Cell-membrane passing imperceptibly into the inter- 
cellular substance. 
