ORIGIN OF LOWEST ORGAXISMS. 45 



that is, dependent upon their properties as living 

 things. These vital movements are altogether dif- 

 ferent from the mere dancing oscillations which not- 

 living particles display, as may be seen when the 

 monad or Bacterium darts about over comparatively 

 large areas, so as frequently to disappear from the 

 field. After an infusion has been exposed for a second 

 or two to the boiling temperature, these vital move- 

 ments no longer occur, though almost all the monads 

 and Bacteria may be seen to display the Brownian 

 movement in a well-marked degree. They seem to 

 be reduced by the shortest exposure to a temperature 

 of 100 C. to the condition of mere not-living par- 

 ticles, and then they become subjected to the unim- 

 paired influence of the physical conditions which 

 determine these movements." I now have various 

 facts to add in confirmation of these conclusions, and 

 in extension of our knowledge concerning the vital 

 resistance to heat of Bacteria and Torulce. 



It would be a most important step if we could 

 ascertain some means by which these primary move- 

 ments of living Bacteria might be distinguished from 

 the secondary, or communicated, movements of not- 

 living particles. In many cases, organisms that are 

 truly living may only exhibit very languid movements, 

 which, as movements, are quite indistinguishable from 

 those that the same Bacteria may display when they 

 are really dead. Because the movements, therefore, 

 are of this doubtful character, persons are apt, unfairly, 



