64 MORPHOLOGY OF THE BACTERIA. 
the same decomposition, of several different forms 
of schizomycetes. On the other hand, in decom- 
positions quite different, we may observe schizo- 
mycetes entirely similar as to their exterior form. 
Finally, we may change the mode of action of a 
schizomycete in subjecting it to a certain treat- 
ment. One sees that it is truly difficult to form 
an opinion as to the value of these species purely 
physiological. 
To sum up, the characters which may be used 
in order to establish genera and species in the 
group of the bacteria are of small number and of 
very unequal value. Some, characters of form, of 
dimension, of movement, etc., are often difficult to 
determine, or have only a relative value; others, 
characters drawn from development and reproduc- 
tion, are only known in so few species that they 
cannot be made to serve as a basis of classifica- 
tion. 
One will not be surprised, then, to find that 
there is no natural classification of the bacteria, 
and that it is impossible for the naturalists to give 
one. All those that can be established are pro- 
visory, being only based upon the morphology of 
these organisms. Following the example of all the 
botanists, we will use an analogous classification, 
but without wishing to prejudge in any particular _ 
the genealogical relationship of the different or- 
ganisms, which we shall consider as distinct gen- 
era and species. 
