332 THE BEGINNINGS OF LIFE. 



particular Bacteria, whilst other evidence points con- 

 clusively in the direction that all Bacteria, whencesoever 

 they have been derived, possess essentially similar vital 

 endowments 1 . Seeing also that the solutions have 

 been inoculated with a drop of a fluid in which Bacteria, 

 Vlbriones, and Tor l^ are multiplying rapidly, we must 

 suppose that they are multiplying in their accustomed 

 manner as much by the known method of fission as 

 by any unknown and assumed method of reproduction. 

 In such a fluid, at all events, there would be all the 

 kinds of reproductive elements common to Bacteria, 

 whether visible or invisible, and these would have 

 been alike subjected to the influence of the same tem- 

 perature. These experiments seem to show, therefore, 

 that even if Bacteria do multiply by means of invisible 

 gemmules as well as by the known process of fission, 



1 The Bacteria and Vibriones with which Prof. Wyman experimented 

 were derived from different sources ; and so far as I, also, have been 

 able to ascertain, the Bacteria of different fluids are similarly affected 

 by exposure to similar degrees of heat. Thus, if on the same slip, 

 though under different covering glasses, specimens of a hay infusion, 

 turbid with Bacteria, are mounted, (a) without being heated, (6) after 

 the fluid has been raised to i22F for ten minutes, and (c) after the 

 fluid has been heated to i4oF for ten minutes, it will be found that, 

 in the course of a few days, the Bacteria under a and 6 have notably 

 increased in quantity, whilst those under c do not become more numerous, 

 however long the slide is kept. Facts of the same kind are observable 

 if a turnip infusion, containing living Bacteria, is experimented with ; 

 and the phenomena are in no way different if a solution of ammonic 

 tartrate and sodic phosphate (containing Bacteria) be employed instead 

 of one of these vegetable infusions. The multiplication of the Bacteria 

 beneath the covering-glass, when it occurs, is soon rendered obvious, 

 even to the naked eye, by the increasing cloudiness of the film. 



