ORIGIN OF LOWEST ORGANISMS. 29 



good for organisms such as Bacteria, which have no 

 chitinous or other envelopes to protect them, and 

 which are merely minute fragments of naked proto- 

 plasm. Having elsewhere* shown how far presump- 

 tions had stolen a march upon established facts, in 

 reference to the supposed possession of a similar pro- 

 perty by the Free Nematoids, my eyes were opened 

 to the reality of this uncertainty with regard to Bac- 

 teria. 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 im- 

 possible to distinguish those which have been added 

 from those which arise in the fluid. Taking into con- 

 sideration the fate of other simple organisms, however, 

 it is by no means improbable that they should be 

 killed even by a short desiccation. I have found, for 

 instance, that desiccation for half-an-hour in a room 

 at a temperature of 65 F. suffices to kill all the larger, 

 naked, lower organisms with which I have experi- 

 mented including long Vibrios, Amaebse, Monads, 

 Chlamydomonads, Euglenae, Desmids, Vorticellse and 

 all other Ciliated Infusoria. 



But, certain indirect evidence seems to speak 

 most authoritatively against the supposition that the 



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



