288 THE BEGINNINGS OF LIFE. 



characteristics, can never be kept too prominently in 

 view especially when the promulgation of all-important 

 doctrines is to hinge upon our decision. 



It should be clearly understood, however, that the 

 question as to the nature of the particles contained in 

 the atmosphere is quite independent of the other en- 

 quiry, whether ciliated Infusoria or Fungi can be evolved 

 in organic solutions without ordinary parentage. 'Bac- 

 teria and some Fungi have been proved by the only 

 kind of evidence which can ever be obtained, to arise 

 de novo j and whilst this proof is possible even by acting 

 on the assumption that the Panspermic hypothesis is 

 true, many of the doctrines of Heterogeny may also be 

 established quite irrespectively of the truth or falsity 

 of the atmospheric germ-theory. It has never been 

 maintained that specimens of the genera Paramecium 

 and Kolpoda are capable of being directly evolved out 

 of a putrescible organic solution. The necessary and 

 invariable preliminary is that innumerable Bacteria 

 should be produced in the infusion, which, by their 

 subsequent aggregation, may form a material out of 

 which the much higher ciliated Infusorial animalcules 

 may be evolved by slow and definite stages, capable of 

 being watched by all skilled microscopists. It would 

 seem, then, even worse than childish to be looking 

 about in the air for germs of these animals. Why did 

 not those who doubted look rather more diligently 

 through their microscopes, to ascertain whether or not 



