318 THE BEGINNINGS OF LIFE. 



believed that none of these organisms survived after 

 they had been similarly subjected to a temperature of 

 60 C; whilst Prof. Wyman, as a result of many ex- 

 periments, always found that their movements entirely 

 ceased after an exposure for a few minutes in fluids 

 raised to a temperature of 54-56C (i3O-J34 c F). 

 There is also every reason to believe, as I shall pre- 

 sently attempt to show, that an exposure to similar 

 conditions kills 'Bacteria as well as their less developed 

 representatives the primordial plastide-particles. 



With reference to Bacteria, however, one caution 

 is necessary to be borne in mind by the experi- 

 menter. Their movements which they display may 

 be, and very frequently are, of two kinds. The one 

 variety differs in no appreciable manner from the 

 mere molecular or Brownian movement, which may 

 be witnessed in similarly minute not-living particles 

 immersed in fluids; whilst the other seems to be purely 

 vital dependent that is upon their properties as living 

 things. These vital movements are altogether different 

 from the mere dancing oscillations which not-living 

 particles display : as may be seen when even the most 

 minute Bacterium darts about over comparatively large 

 areas, so as frequently to disappear from the field 

 of the microscope. After an infusion which contains 

 organisms exhibiting these unmistakeably vital move- 

 ments has been boiled for a second or two, I have 

 invariably found that such movements no longer occur, 

 though almost all the plastide-particles and Bacteria may 



