GENERAL MORPHOLOGY AND PHYSIOLOGY. 125 



ment throughout the whole of their life history. 

 Others, during certain stages of their life cycle, and 

 possibly some forms always, are endowed with 

 locomotive power. The character of the movement 

 is very varied, and ranges from a slow undulatory 

 motion to one of extreme rapidity. Many appear 

 to progress in a definite direction. Others move 

 continuously, first in one direction and then in 

 another, and others again seem to hesitate before 

 ..altering their course. They may either glide along 

 smoothly or progress with a tremulous action. 

 They appear to be able to avoid obstacles, and to 



FIG. 50. SPIROCH^TA FROM SEWAGE WATER, x 1200. 



set themselves free from objects with which they 

 have accidentally come into contact. Vibrios have 

 a peculiar serpentine movement, but other forms, 

 such as the commonly-known Bacterium termo and 

 segments of spirilla, such as comma-bacilli, revolve 

 around their long axis as well as make distinct 

 progression. The comlpete spirilla are charac- 

 terised by the familiar corkscrew movement. 

 With regard to cocci there is some doubt as to 

 whether they are endowed with independent move- 

 ment; any quivering or oscillation is generally 

 regarded as only brownian or molecular. In some 



