THE BEGINNINGS OF LIFE. 295 



manner above mentioned, it is not difficult with the 

 stage of the microscope in a horizontal position 

 to bring into the field of view a portion of the film, 

 which either contains no visible 1 particles, or only 

 a small number, such as can be easily counted. With 

 the slip resting on one of Strieker's hot-water plates 

 maintained at a temperature of 85-95 F., it may be 

 found that, in the course of three or four hours, faint 

 and ill-defined whitish specks, less than 5 - J 00 " in 

 diameter, make their appearance pretty evenly dispersed 

 throughout the field of view. These are at first almost 

 motionless exhibiting only the merest vibrations, but 

 no progressive movements. They gradually become 

 more distinct, assume a sharper outline, and after 

 a variable time some of them develop into distinct 

 'Bacteria 2 . At first they exhibit gentle oscillations and 

 tremblings only, though gradually they display the more 

 characteristic darting movements. The study of the 

 mode of origin of these primordial living forms is, in- 

 deed, facilitated and rendered much more certain by the 

 fact that they remain comparatively motionless for a 

 long time after their first appearance, and also continue 

 faint and much less refractive than when in the more 

 mature condition. Hence it becomes a matter of the 



1 Working with a magnifying power of 1000 diameters. 



2 The shortest time in which I have seen Bacteria develop in such 

 a film has been one hour and a half. More frequently, however, three 

 hours have elapsed, and sometimes longer still, before distinct Bacteria 

 have made their appearance in the field of view. 



