60 ORIGIN OF LOWEST ORGANISMS. 



also that the solutions have been inoculated with a drop 

 of a fluid in which Bacteria, Vibr tones, and Torulcz 

 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 temperature. 

 These experiments seem to show, therefore, that even 

 if Bacteria do multiply by means of invisible gem- 

 mules as well as by the known process of fission, such 

 invisible particles possess no higher power of resisting 

 the destructive influence of heat than the parent 

 Bacteria themselves possess. This result is, more- 







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, (8) after the fluid has been raised to 

 122 F. for ten minutes, and (c) after the fluid has been heated to 

 140 F. for ten minutes, it will be found that, in the course of a 

 few days, the Bacteria under a and b 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 observ- 

 able if a turnip infusion, containing living Bacteria, is experi- 

 mented 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. 



