ORIGIN OF LOWEST ORGANISMS. 33 



just the same amount of actual evidence for believing 

 that they have been formed de novo, as we should 

 have for believing that crystals had been formed de~ 

 novo, if we had seen them appearing under our eyes in 

 the same manner. Whether they really arise after the 

 fashion of crystals, without the aid of pre-existing 

 though invisible germs, is a matter which can only be 

 settled inferentially, by a subsequent resort to strict 

 methods of experimentation. 



Seeing however, that we are able, with the aid of 

 the microscope alone, to demonstrate that Bacteria 

 and Torulcz can develop in situations where no visible 

 germs had previously existed, it is useless, as I have 

 said before so far as the question of their mode of 

 origin is concerned to search the atmosphere to ascer- 

 tain what visible germs it may contain. If some Bac- 

 teria and Tor nice arise from germs at all, it must be 

 from germs which are invisible to us. The finding of 

 visible germs in the atmosphere can, therefore, only 

 have an indirect bearing upon the solution of the pro- 

 blem. Since it can be shown that some visible spores 

 and ova exist in the atmosphere, this affords a certain 

 amount of warrant for the supposition that invisible, 

 living, reproductive particles may also exist more 

 especially if the existence of an amount of organic 

 matter, which is ordinarily invisible, can be revealed 

 in the air, by the agency of the electric beam, or by 

 any other means. 



Nothing can be more illegitimate, however, in the 



D 



