OF ANIMALCULES. 101 



GENUS X. 



BURSAR I A. 



" A SIMPLE, hollow, membraneous animalcule/' which 

 takes its name from its bag or purse-like form. Ehren- 

 berg has only noticed one species, and has not decided 

 as to the situation of the genus. 



172. BuRSARiA truncatella. The truncated Bursaria, — 

 This animalcule is discernible by unassisted vision, when 

 it appears of a milk-white hue : the diameter of some 

 fine specimens which I measured was l-50th of an inch. 

 Its form is shewn at figure 99, the cross denoting the 

 mouth-aperture of the bag-like membrane. At the pos- 

 terior extremity may be seen several small globular bo- 

 dies : these were considered to be ova by MuUer ; but 

 as I have seen this animalcule swallow the smaller 

 species of the Volvox, and also the Gonimn pectorale, I 

 feel assured he must be mistaken. In swimming they 

 sometimes revolve, at others they move alternately from 

 one side to the other, in constant search of prey. 



173. Bursaria bullina. The bubble Bursaria, — This 

 species is shewn at figure 100, slightly magnified ; it has 

 some resemblance in form to a boat. It is pellucid, and 



