INFUSORIA. 133 



herent to Ceratophyllum and other plants with finely 

 divided leaves. Every part should be searched with the 

 microscope, especially the angles between the leaflets. 



The bodies of the Infusoria are usually very soft 

 and delicate. Some of them are so flexible that they 

 can double and twist themselves almost as well as a 

 worm. Others are hard, and some are even covered by 

 a transparent case secreted from their own body. This 

 case is called a lorica, and is used as a shelter for the 

 soft and otherwise defenceless animal. When fright- 

 ened it quickly withdraws itself to the bottom of the 

 lorica, and remains there in a little, almost shapeless, 

 heap, until the danger is past. Then it slowly rises up 

 to the front of the lorica, protrudes the front part of 

 the body, opens the organs by which it creates currents 

 in the water,, and so fishes for the food those currents 

 bring to its mouth. These loricae are usually perma- 

 nently attached to plants or other submerged objects. 

 They are also generally transparent and colorless, but 

 sometimes, as they become old, the color changes to a 

 rich, translucent chestnut brown. In other Infusoria 

 the loricse are not hard and transparent, but soft and 

 delicate. These are usually made of innumerable little 

 particles of dirt fastened together by a sticky substance 

 secreted from the animal's body. Almost any small 

 particles floating about and striking against the sticky 

 mass will be quite sure to adhere, and so help build up 

 the soft sheath that serves the Infusorium as a protect- 

 ive covering, and sometimes effectually conceals it from 



