INFUSORIA. 



151 



contraction of the branches and of the stem will dis- 

 tinguish it from all other tree-like Infusoria. 



3. Epistylis (Fig. 108). 



As in the two preceding, the stem of Epistylis is 

 often much branched. The Infusoria at the ends of 

 the branches can alone contract, which they often do 

 with a jerk, settling back on their stalk as if they 

 meant to impale themselves, or dropping and nodding 

 like flowers fading on their stems. The bodies of the 

 expanded animals 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 with a high-power objective. 

 The one-inch lens, however, will 

 show the rapid currents produced, 

 because all small particles in their 

 neighborhood are caught up and 

 dashed around in the mimic whirl- 

 pools. The animals select from these 

 streams anything which they may 

 want and let the rest sweep by; they 

 have a distinct mouth near the center 

 of the frontal region. The- entire colony is usually 

 colorless. It is often found attached to Cerato- 

 phyllum. 



4. VORTIcfiLLA (Fig. log). 



The unbranched stem of Vorticdla contains a spiral 

 muscular thread like a thin cord, which with surprising 

 suddenness contracts into close coils, and draws the 

 Infusorium down with it, the bell-shaped body con- 

 tracting at the same time into a spherical mass. 



Fig. 108. — Epistylis. 



