102 NATURAL HISTORY 



its anterior is occasionally occupied with several very 

 small glass-like sphericals. Found in sea-water. 



174. BuRSARiA hyrundinella. The little swallow-like 

 Bursaria, — The form of this animalcule, by a little 

 eiFort of imagination, may be compared to a bird, and 

 its movements appear like the flight of the swallow: 

 hence its name. It is smaller than the two preceding 

 species. A magnified view of it is shewn at figure 101. 

 It is found in stagnant water. 



175. Bursaria duplella. The folded Bursaria. — This 

 species is rather scarce, concealing itself under duck- 

 weed. It is a hollow membrane, folded, as shewn in 

 figure 116, with an opening left between the edges the 

 entire length of the animalcule. 



176. Bursaria glohina. The globular Bursaria. — 

 This animalcule is of a globular form : the interior is 

 sometimes occupied by dark spherules ; in other speci- 

 mens longitudinal markings may be discerned on the 

 body, as shewn at figure II7. 



