62 MORPHOLOGY OF THE BACTERIA. 
all true, he says, of the spirilla, which are not only 
distinguished from the rod bacteria, properly so 
called; but which present in their species some 
differences as constant as any well-defined species 
of alga or of infusoria. 
Hallier, Hoffmann, Billroth, Robin, Nagel, etc., 
consider the different forms of bacteria in a very 
different fashion. According to them they are 
not autonomous species, but phases of development 
of one or of several species. 
According to Hallier, we may see, @ propos of 
the polymorphism of the bacteria, the singular 
transformations which he has obtained by their 
cultivation. 
According to Billroth, the bacteria belong to a 
single species of plants, the Coccobacteria septica, 
with the exception of the Spirillwm and Spirocheta, 
in regard to which Billroth is not willing to give 
an opinion. This view has been adopted by a 
certain number of microscopists, and above all by 
the pathologists, such as Frisch, Tiegel, etc. 
Robin also admits the genetic relation of Micro- 
coccus, Vibrio, Bacterium and Leptothrix, but con- 
siders them the distinct and successive phases in 
the evolution of several species: Ist. Corpuscles 
described under the name of Bacterium termo, 
punctum, ete., Micrococcus ; 2d. Mycelial fila- 
ments, Vibrio, etc.; 3. Bacteria, Bacteridies, Micro- 
bacteria, etc.; 4th. Leptothrix and forms more 
advanced. 
The opinion of Niageli corresponds very nearly 
with the preceding. “As much as I am con- 
