28 ORIGIN OF LOWEST ORGANISMS. 



Although, therefore, no direct evidence has been 



^5 ' 



adduced tending to show that Bacteria are present 

 in the atmosphere, even if this evidence had been 

 forthcoming, it would have been necessary, in reference 

 to M. Pasteur's hypothesis, for it to be supplemented 

 by further evidence to the effect that Bacteria were 

 well capable of resisting such an amount of desiccation 

 as must have been involved by their presence for an 

 indefinite time in the atmosphere even of the hottest 

 and driest regions of the earth. For, organic sub- 

 stances in solution do not only putrefy in moist 

 weather or moist climates ; they putrefy most rapidly 

 and surely when the temperature is high, and quite 

 irrespectively of the amount of moisture contained 

 in the atmosphere. A property of resisting the 

 effects of desiccation the possession of which, by 

 Bacteria, is so necessary for the truth of M. Pasteur's 

 argument ought to have been shown by scientific 

 evidence to be a real attribute of such organisms ; 

 though it seems, on the contrary, to have been 

 assumed to exist, with almost equal readiness by both 

 parties, in the controversies concerning the possibility 

 of " spontaneous generation." This error may be 

 ascribed to the misguiding influence of a treacherous 

 analogy. Whilst it may be true that certain seeds 

 and spores, and also that Rotifers, " Sloths," and some 

 Nematoids are capable of resisting the influence of a 

 prolonged exposure to desiccating influences, it may 

 well be asked, whether the same fact necessarily holds 



