THE BEGINNINGS OF LIFE. 



assumed to exist by nearly all those who have taken 

 part in the controversies concerning the possibility of 

 'spontaneous generation.' This error may again be 

 ascribed to the misguiding influence of a treacherous 

 analogy. Whilst it may be true that certain seeds 

 and spores, and also that Rotifers, ' Sloths,' and some 

 Nematoids are capable of resisting the influence of a 

 prolonged exposure to desiccating influences, it may 

 well be asked, whether the same fact necessarily holds 

 good for organisms such as Bacteria^ having no chi- 

 tinous or other envelopes to protect them, and which 

 are merely minute fragments of naked protoplasm. 

 Having elsewhere ^ shown how far presumptions had 

 stolen a march upon established facts, in reference to 

 the supposed possession of a similar property by the 

 Free Nematoids, my eyes were opened to the reality 

 of this uncertainty with regard to Bacteria. It is, 

 however, no easy matter definitely to prove or to 

 disprove the possession of this property by organisms 

 so minute as Bacteria^ and therefore so difficult to 

 identify. If dried Bacteria are added to a drop of a 

 suitable solution — similar to that in which they had 

 been bred — it soon becomes quite impossible to dis- 

 tinguish those which have been added from those which 

 arise in the fluids. Taking into consideration the 



^ 'Philosophical Transactions,' 1866, pp. 616-619. 



2 And similarly if we introduce dried Bacteria into a solution which 

 will nourish them, although it had previously no tendency to breed them 

 de novo, and Bacteria are subsequently produced, we cannot safely affirm 



