DEVELOPMENT OF THE BACTERIA. 101 



is the first question which presents itself, a ques- 

 tion which has given rise to long discussions, in 

 the examination of which we shall only enter in 

 order to give a short historical statement. 



1. ORIGIN OF THE BACTERIA. 



The origin of the bacteria, as of all the other 

 inferior organisms, is conceived in three different 

 manners : 



1. For some, these organisms are produced by 

 heterogenesis ; that is to say, by creation outright 

 from mineral or organic substances (spontaneous 

 generation). 



2. According to others, they come directly from 

 individuals like themselves, by one of the known 

 modes of generation, fission, spores, etc. 



3. Finally it is believed that they are derived 

 from organisms already existing, and are nothing 

 more than different states or phases of develop- 

 ment of known species, of which the life cycle is 

 not 'yet discovered. 



We will examine the latter hypothesis, which 

 constitutes what is called polymorphism, when we 

 speak of the phenomena of reproduction. 



As to the two first, we will content ourselves 

 with indicating the late works which have appeared 

 for and against each; insisting above all upon the 

 facts which relate to the proof of the presence of 

 bacteria or their germs in the air, water, and 

 liquids or tissues of the. human organism, blood, 

 urine, etc. 



