142 MICROSCOPY FOR BEGINNERS. 



branches and the stem will distinguish it from all other 

 tree-like Infusoria. 



3. EPISTYLIS (Fig. 103). 



As in the two preceding, the stem of Epistylis is 

 also often much branched. The Infusoria at the ends 

 of the branches can alone contract, which they often do 

 with a jerk, settling back as if they meant to impale 

 themselves, or dropping and nodding like flowers fad- 

 ing on their stems. The bodies of the expanded ani- 

 mals are somewhat bell-shaped, their widest part being 

 the free end which closes when the body contracts. 

 The front border is encircled by a row of 

 cilia, to be properly discerned only by a 

 high-power objective. The one-inch glass, 

 however, will show the rapid currents pro- 

 duced, because all small particles in their 

 neighborhood are caught up and dashed 

 around in the mimic whirlpools. The ani- 

 mals select from these streams anything 

 they may want and let the rest sweep by. 

 They have a distinct mouth near the centre 

 of the front part. The entire colony is usually colorless. 

 It is often attached to Ceratophyllum. 



4. VORTICELLA (Fig. 109). 



The unbranched stem of Vorticella contains a zigzag 

 muscular thread like a thin cord, which contracts into 

 close coils very suddenly, and draws the Infusorium 



