15° 



AQUATIC MICROSCOPY FOR BEGINNERS. 



.-_^ , 2. CARCHfislUM (Fig. 107). 



The stem, attached to. plants or to other submerged 

 objects, is divided at the summit into many branches, 

 with one Infusorium at the end of each, and many- 

 others scattered along them with shorter branches of 

 their own. Through the main stem and through all 



the branches extends 

 a cord-like muscular 

 thread that suddenly 

 contracts when the 

 animals are frightened 

 or disturbed, and 

 pulls the entire colony 

 down toward the point 

 of attachment to the 

 plant. But each 

 branch may contract 

 one at a time and 

 draw its burden of_ infusorial fruit down to the main 

 stem without disturbing any other portion of the col- 

 ony; or all the.branches may contract at the same time. 

 Therefore, while the individual animals are connected 

 together, they are still somewhat independent. 



The ifront border of each body is surrounded by a 

 circle of cilia visible under a high power. They are 

 the only cilia on the creatures. When the animal is 

 contracted these cilia are folded together, each body 

 then resembling a little ball. They vibrate rapidly, 

 producing circular currents that bring to the mouth 

 any food particles which may be in the vicinity. 



The entire colony is colorless, and may include as 

 many as a hundred Infusoria on the branches. It can 

 be seen with a low power objective. .The independent 



Fig. 107. — Carch^sium. 



