152 



AQUATIC MICROSCOPY FOR BEGINNERS. 



The Vorticellas are common, scarcely a leaflet of 

 any aquatic plant being without them. They are usu- 

 ally colorless, although green ones do occur. The 

 body is bell-shaped, the narrow part of the bell being 

 fastened to the top of the contractile stem. The front 

 border is surrounded by a circle of fine cilia which 

 need a high power to show them. These produce 

 currents in the water similar to those of Epistylis, and 

 for the same food-collecting purposes. 



The contractions of the stem 

 are surprising in their sudden- 

 ness. While the observer is 

 quietly gazing at the graceful 

 creature whirling its cilia and 

 making tremendous whirlpools 

 on a small scale, it disappears 

 like a flash, and the student feels 

 like looking for it on the table. 

 But presently it begins to rise 

 slowly from the plant against 

 which it was crouching, and the 

 spirally coiled stem lengthens as 

 it straightens. Frequently it is hardly extended be- 

 fore it again leaps out of sight, or close to the object 

 that supports the stem. 



This, will probably be one of the first Infusoria to 

 attract the beginner's attention, and he will think it a 

 wonderful thing, as it is. The figure (109) shows 

 some extended and some contracted. They are often 

 found in clusters, sometimes of a hundred or more, all 

 bobbing and swaying in a laughable way, for when one 

 contracts it usually sets them all off. 



Fig. log. — Vortic^Ua. 



