126 PHYSIOLOGY OF THE BACTERIA. 
cation being continued with the same conditions, 
the bacteria issuing from a single germ would fill 
the ocean in five days.” 
Reproduction by Spores.—The multiplication 
by fission, known to the earliest microscopists, has 
been until recently the only mode of propagation 
admitted by the ‘authors. Thus M. de Lanessan, 
in the excellent article which he has devoted to 
the bacteria, says that the marvellous resources of 
modern science have not yet permitted us to rec- 
ognize any other mode of propagation for these 
organisms. 
However, M. Ch. Robin had already, in 1853, 
indicated the presence in Leptothriz buccalis of 
little round bodies, “ which are perhaps spores.” 
Pasteur has since, in 1865, recognized that “ the 
vibrios of putrefaction and of butyric fermentation 
present a sort of ovule, or ovoid corpuscle, which 
refracts light strongly, either in the extremity 
or in the body of the articles.” Later, the same 
savant, more explicitly, says clearly that these or- 
ganisms have two modes of reproduction, — by 
fission and by interior spores (“‘ noyaux”’). 
Towards the same epoch, Hoffmann also pointed 
out a reproduction by free cellular formation in 
some bacteria. But we must come to the labors 
of Cohn, Billroth, and Koch, in order to find pre- 
cise observations in this regard. 
The formation of spores has been observed 
in Bacillus subtilis by Cohn, Bacillus anthracis 
by Koch, and in Bacillus Amylobacter by Van 
Tieghem. 
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