INFUSORIA 461 



of an oval disk, which, when seen sidewise, is found to 

 be flat beneath and convex above. It commonly swims 

 with the belly upward, and when exhibited on the stage 

 of the microscope, in almost every case, this surface is 

 presented to the eye. ft darts about very irregularly, with 

 a bobbing motion, rarely going far in one direction, but 

 shooting a little distance, and then instantly receding, 

 turning short round, and starting hither and thither, so 

 fitfully that it is very difficult to obtain a fair sight of its 

 structure. Its margin, however, is surrounded by short 

 cilia; the mouth, which is a long opening on the front 

 part, and at the left side (as to the animal) of the ventral 

 surface, is fringed with long cilia, which are continually 

 vibrating. These are the organs of the darting motion; 

 but the creature crawls like a mouse, along the stems of 

 conferva, etc., which it performs by means of curved spines, 

 called uncini, near the front part, the points of which are 

 applied to the stem, and also by long stiff styles, or bris- 

 tles, which project backward and downward from the 

 hinder part. Sometimes the animalcules crawl for a mo- 

 ment back-downward, on the inner surface of the glass 

 cover, when the bases of the anterior curved spines appear 

 dilated like large spots. The spines are not capable of 

 much action, but they are rapidly used. The general 

 appearance of the creature reminds us of the little Wood- 

 louse or Armadillo of our gardens. The interior of the 

 body is occupied with a granular substance, in which are 

 scattered many globular vesicles of different sizes. The 

 animal is very transparent, and almost colorless. They 

 increase very fast by transverse division which is per- 

 formed under the microscope, so as greatly to increase the 

 number under examination even in an hour or two. A 



