ORGANIZATION OF THE BACTERIA. 31 
Color. — The phenomena relating to the color 
of bacteria have only recently been pointed out. 
‘“‘ But little attention has been given to the color 
of the bacteria, regarded generally as colorless,” 
said M. de Seynes in 1874; and recently M. de 
Lanessan, ‘‘ The bacteria are ordinarily quite color- 
less.’ However, M. Cohn had already insisted 
upon the globular bacteria chromogeénes, or of pig- 
mentary fermentation, and upon the colors pro- 
duced by different monads, which have long since 
been studied by microscopists. 
Upon this subject, let us observe that the bac- 
teria which are colored belong to two very dif- 
ferent groups. First, colored organisms always 
known as such, but which were not formerly in- 
cluded with the bacteria, as the different monads, 
which have become the Micrococcus prodigiosus, 
cyaneus, aurantiacus,Cohn, etc.; the second group 
includes the bacteria properly so called, which 
absorb the coloring matter of vegetables upon 
which they are fixed as parasites, or of the media 
in which they live. This is the case with the bac- 
teria observed by M. de Seynes upon the Peniev- 
lum glaucum, and perhaps with the Vibrio syn- 
zanthus and syncyanus, Ehrenb., which give to milk 
a yellow or blue color according to the species. 
We will return to this subject when we speak of 
the nutrition of the bacteria. 
As to the purple-colored monads, they have 
been especially studied as early as 1838 by Dunal, 
then by Morren and Ehrenberg, and in our own 
day by Ray-Lankester, Cohn, Klein, and finally 
