ORIGIN OF LOWEST ORGAXISMS. 



The possible modes of origin of Bacteria and 

 Tonilce may, therefore, be tabulated as follows :- 



f a. Direct. 

 Modes of origin f i- Homogenesis. j ^ indirect. 



of Bacteria and < 2 . Heterogenesis. 

 70^- I 3. Archebiosis. 



i. HOMOGENETIC MODE OF ORIGIN OF BACTERIA 



AND TORUL/E. 



Bacteria and Tonilcs being already in existence, 

 they may, undoubtedly, reproduce organisms similar 

 to themselves by processes of fission and gemma- 

 tion in the same way that other low protistic 

 organisms propagate their kind. Although so many 

 reasons rendered this view probable, it was some 

 time before I was able actually to confirm it by 

 personal observations in the case of Bacteria. In the 

 ordinary microscopical examination of portions of an 

 infusion containing these organisms, an observer may 

 watch for hours and never see a single instance of 



o 



such fission occurring. His attention is apt to be dis- 

 tracted by the number of organisms which are con- 

 stantly flitting before his view, and he is, moreover, 

 perhaps apt to pay particular attention to those which 

 seem by their movements to be most obviously alive. 

 I have observed the process most plainly when a 

 few Bacteria have been enclosed in a single drop of 

 fluid, pressed into a very thin stratum, in a " live-box ' 

 kept at a temperature of about 90 Fahr. by resting 



