WHAT is LIFE? 15 



cules which presented this appearance. By feeding with 

 coloring matter, as carmine or indigo, these stomachs 

 have been found to be merely excavations in the bio- 

 plasm, or living matter, which constitutes the body ot 



r^iG. i. a. Colony of Vorticella. b. b. b. Stages of fission, or self-division, c. A sep- 

 arate individual, d. Encysted state, e. Ruptured cyst emitting gemmules in a mass of 

 gelar'ne or gum. f. Acineta parasites. 



tht: animal. Some of these excavations are extempo- 

 raneous, but one cavity is persistent, and pulsates in a 

 peculiar manner, so that it has received the name of 

 contractile vesicle. Each glassy bell is attached to the 

 twig by a slender thread, and usually swings to and fro 

 in the water with the thread or footstalk fully stretched, 

 and the cilia moving rapidly. Frequently, however, and 

 especially on some unusual jar, or other cause of alarm, 

 the thread contracts in the form of a spiral, and the cilia 

 are withdrawn into the substance of the bell. 



These Infusoria usually increase by self-division. The 



