296 THE BEGINNINGS OF LIFE. 



greatest ease to watch their appearance in thin films of 

 fluid, and also to distinguish them from other extraneous 

 particles with which they may coexist. 



But if, in a motionless film of fluid, multitudes of 

 living particles subsequently appear, which are them- 

 selves almost motionless, how can we account for 

 their origin? Three hypotheses present themselves. 

 It may be said (a) that they have arisen through the 

 reproductive multiplication of one or more germs or 

 organisms in the film of fluid which, though visible^ 

 had escaped observation. The difficulties standing in 

 the way of our acceptance of this explanation are these. 

 The film is motionless, and also those first appearing 

 particles which gradually come into view in portions 

 of it where no such particles had been previously 

 visible. No multiplication by fission or other means 

 can actually be observed to take place by microscopists 

 among the mere particles in question, though this ought 

 to be easily observable if it really occurred at the rate 

 postulated. And lastly, if the subsequent large numbers 

 are to be accounted for by the occurrence of a repro- 

 ductive process taking place amongst a few visible but 

 unobserved germs, these products of fission, being mo- 

 tionless, ought to be aggregated here .and there only 1 , 

 whilst as a matter of fact, no such arrangement exists 

 there is rather a uniform diffusion of the particles. These 



1 This does actually take place in the appearance of Torula cells in a 

 watch-glass (p. 281), because, being also motionless, they do undergo a 

 rapid process of subdivision, even whilst they are of a very minute size. 



