THE BEGINNINGS OF LIFE. 213 



puscles which still display almost unaltered Bacteria 

 imbedded in their substance : generally, however, the 

 corpuscles which separate from the pellicle in this 

 comparatively unaltered condition, undergo certain 

 slow changes before the flagellum is developed. The 

 contained Bacteria become more and more indistinct, 

 whilst the substance of the corpuscle grows rather more 

 refractive and assumes the appearance of ordinary proto- 

 plasm. Corpuscles about -5 oVo" in diameter are often 

 very obscurely granular and quite motionless. They 

 grow, however, and when they have attained the size 

 of ^oVo'' in diameter they frequently begin to exhibit 

 slow undulating alterations in outline, and tend to 

 assume an ellipsoidal form. One specimen 33V0'' in 

 diameter, was seen without a flagellum_, but slowly 

 alternating between the spherical and ellipsoidal forms. 

 Suddenly, at one extremity of the ellipsoid, a series 

 of rapid contractions and protrusions of its substance 

 were observed, and when they ceased, a motionless 

 filament was seen bent around one side of the body. 

 Three minutes afterwards a vacuole appeared for the 

 first time at the opposite extremity of the ellipsoid. 

 The corpuscle remained almost motionless for twenty- 

 five minutes, merely exhibiting very slight changes in 

 outline ; after thirty minutes the first slow bendings of 

 the flagellum were seen; and after thirty-five minutes 

 the whole organism began to exhibit slow semi-rotations 

 at intervals of a minute or two. After forty minutes 

 the movements were pronounced and of a startling 



