14 THE GENERAL CHARACTERS OF MICROORGANISMS. 
much smaller number of species. It is frequently uncertain whether 
a species described by one bacteriologist is the same as that de- 
scribed by another under the same name. The difficulties in the 
way of a proper description and classification of the species of 
bacteria have hitherto been insurmountable, and at the present 
time the subject is in such extreme confusion that no one except an 
expert can understand it. Fortunately this confusion of species 
is of no importance for our purpose. Agricultural bacteriology is 
not at present concerned with the problem of the species. All that 
it is necessary for us to know in connection with our subject will be 
referred to in the separate sections in the following pages, and the 
subject of the classification of bacteria may be left without further 
consideration. 
Multiplication of Bacteria. As already mentioned, the 
primary method of the multiplication of bacteria is by simple 
division. Bacteria are so minute that it seems strange to assign 
to them much of a part to play in nature's processes. But their 
extraordinary power of multiplication gives them unlimited possi- 
bilities. 
The elongation of a rod and its division into two parts, followed 
by a repetition of the process, may be extremely rapid. Frequently 
it does not take more than half an hour for the whole phenomenon 
to take place, and sometimes even less time is required. Such 
division, in geometrical ratio, results in an increase in numbers 
that is almost inconceivably great. If a division once an hour 
could be maintained for twenty-four hours, there would be pro- 
duced, as the offspring of a single bacterium, some seventeen million 
descendants, and in five days there would be a mass sufficient to fill 
the oceans. This rate is, manifestly, not continued for any great 
length of time, or the world would be full of them; their growth is 
checked by lack of food, and still more by the substances they se- 
crete, which act as poisons. But this possibility of reproduction 
represents an almost unlimited power, constantly curbed by the 
lack of proper conditions. Bacteria may thus be looked upon as 
possessing a wonderful possibility of reproduction, a force of in- 
conceivable magnitude, held more or less in check by adverse condi- 
