164 THE AMERICAN NATURALIST [Vol. LI 



The body of Loxophyllum (Fig. 6) is surprisingly elas- 

 tic. For this reason the creature undergoes rapid varia- 

 tions in length. Even within the confinement of a viscous 

 gelatin solution which checks the motions of all of the 

 other ciliates its strength is such as to enable it to per- 

 form various evolutions over the slide. In staining it fre- 

 quently dies in a contorted and contracted condition. 

 Before staining, it should be narcotized with a weak ethyl 

 alcohol or killed with .01 per cent, osmic acid. 



In Astasia (Fig. 7) the smaller secondary flagellum is 

 sometimes either unusually filamentous, and therefore in- 

 visible, or lacking altogether. In many individuals no 

 amount of manipulation of light directions and intensities 

 -or stains will reveal the smaller flagellum. 



Urocentrum turbo (Fig. 8) can always be recognized by 

 the frenzied and jerky rotation which accompanies its ex- 

 i;remely rapid movement through the water. It usually 

 ^omes to rest either close beside or buried among masses 

 of algae or other convenient material. In this resting con- 

 dition it is liable to be overlooked. At such times its only 

 evidence of activity is a scarcely perceptible twitching. 

 This hiding in algal masses has all the appearance of being 

 a deliberate attempt at concealment. Suddenly without 

 warning its crazied rotation through the water is begun 

 again. When swimming with retarded velocity through a 

 gelatin solution, functional anterior and posterior por- 

 tions of the body are recognizable. 



Envieonmental Type No. II: Clear Cold Waters 

 Lacking Plant Growths 

 Sediment, composed of quartz and shale sands free from 

 • organic silt and supporting no plant life save a few Dia- 

 toms, in clear, pure, cold lakes and streams ; temperature 

 . of water, cir. 56° F. 

 Predominant forms : 



Nostolenus sp., several 



