THE BEGINNINGS OF LIFE. 299 



similarly exposed vessel of distilled water. But on the 

 other hand, the state of our knowledge concerning the 

 rapidity with which these animals multiply by fission 

 and by the still more exceptional sexual method of 

 reproduction is, in turn, equally opposed to such a 

 notion. 



Moreover, even if we had not the above-mentioned 

 evidence of the test vessel, the investigations of 

 M. Pasteur as well as those of M. Pouchet would de- 

 cidedly lead us to reject the notion that any small 

 portion of air contains a plurality of dried Infusoria or 

 of their germs. The refractive granules and supposed 

 germs (^corpuscles organises') are of much smaller 

 size, and are presumed by M. Pasteur himself to re- 

 semble the spores of fungi rather than the much larger 

 and much more definitely constituted germs or dried 

 bodies of Infusoria. He does not pretend to say that 

 these are abundant in the atmosphere, or that they are 

 to be met with in any appreciable number in a limited 

 volume of ordinary air. 



Again, the evidence above-cited and that which the 

 microscopist can supply is supplemented by the fact 

 that the pellicle must always be of an appreciable 

 thickness in order that ciliated Infusoria may be pro- 

 duced. Unless this is the case, such organisms are 

 not to be found in the infusion after the accustomed 

 time; or perhaps they may never occur at all, however 

 long a period has elapsed. This has been clearly enough 

 ascertained by the very simple but ingenious experi- 



