304 THE BEGINNINGS OF LIFE. 



than upon that of microscopic Fungi or Alg^. We have 

 done this for several reasons. In the first place, the 

 germs of Fungi are very minute. Many of them 

 are merely small, spherical, translucent, but structure- 

 less bodies^ so that it is often a matter of difficulty, 

 on microscopical evidence, to decide between them 

 and other corpuscles which, though they may present a 

 similar appearance may really be quite different in 

 nature. Again, the origin of Fungi and of Algas in 

 organic and other infusions, by a process of Archebiosis, 

 had already been established ^, so that we knew more 

 about the possible modes of origin of these than con- 

 cerning the modes of origin of Ciliated Infusoria. And 

 lastly, because even M. Pasteur himself is unable to 

 say that he has found amongst his particles obtained 

 from the atmosphere many dried bodies of ciliated In- 

 fusoria, either in their ordinary or in their encysted 

 condition — or even the ova of these organisms. All 

 are agreed that such things are only exceptionally met 

 with amongst the debris obtained from filtration of 

 the atmosphere, and no one has yet hazarded the 

 opinion that such ciliated Infusoria are capable of 

 originating from aught else derived from the atmo- 

 sphere but the revived though previously dried bodies 

 of such organisms, or from their ova. No one has 

 propounded the theory that ciliated Infusoria are de- 

 rived from invisible germs, or from ova other than 

 those of known size and appearance. 



^ By Experiments recorded in Chaps, ix. and xi., and in Appendix C. 



