74 DROPS OF WATETl. 



transparent ; a few, also, are of a golden yellow. 

 N. viridis (Drop I. fig. 14), N. amp/iisbtena- (fig. 

 15), and N. acus (fig. 16), are frequently seen. 



The genus Bacittaria, from which the family 

 derives its name, is composed of bodies of sin- 

 gular construction. They seem originally to form 

 connected lines, but, when mature, separate gene- 

 rally only in part, forming zigzag chains : in this 

 state they move slightly, and one marine species, 

 B.paradoxa, when separated from its compa- 

 nions, moves quickly like a Navicula. B. vulgaris 

 (Drop I. fig. 17) is by many botanists looked 

 upon as a vegetable, and named Diatoma floccu- 

 losum : it is found both in fresh and salt water, 

 and has a straight lorica three or four times as 

 long as broad ; and when seen sideways it is in 



