HISTORICAL. ler 
exception in favor of the cilia, of which the ex- 
istence has been recently verified in the case of 
several of the bacteria by divers botanists, among 
others by MM. Cohn and Eug. Warming. 
Dujardin (1841), in his “ Histoire Naturelle des 
Zoophytes,” preserved the family of the vibrioni- 
ens of Ehrenberg among the infusoria, characteriz- 
ing them as follows: “ filiform animals, extremely 
slender, without appreciable organization, without 
visible locomotive organs.” He made but few 
modifications, of which the principal consisted in 
uniting Spirocheta with Spirilum, Dujardin. Re- 
jecting the character that Ehrenberg drew from 
the rigidity of the spirilla, the Spirocheta plica- 
tilis, Ehrb. became the Spirillwm plicatile, Duj. ; 
but, as will be seen later, this change has not 
been maintained. Dujardin, then, classed the bac- 
teria in: 
1. Bacterium: filaments rigid, with a vacillating 
movement. 
2. Vibrio: filaments flexible, with an undulatory 
movement. 
3. Spirillum: filaments spiral, movement rotary. 
Until this time the bacteria had been considered 
as animals placed at the foot of the series. Sub- 
sequently the tendency to place them in the 
vegetable kingdom became more and more pro- 
nounced. 
Already, since 1853, M. Ch. Robin had pointed 
out the relationship of the bacteria and of the 
2 
