CLGSTERIUM. 



67 



near the ends, with a high magnifying power, 

 a transparent spot, containing minute granules 

 in constant motion. Some species are smooth, 

 others striated but this is rarely seen, excepting 

 when the case is emptied of its green matter. 

 The method of increase is very similar to that 

 described in other genera, but differs in some 

 degree. The pale line in the centre becomes 

 double, the intermediate portion gradually in- 

 creases, and then another transverse line becomes 

 visible in its centre ; when mature, complete 

 separation takes place there, and two Closteria 

 are formed. The species are above twenty. 

 C. aceromm (Drop I. fig. 8) is a very pretty 

 object, bright green, and very slender in form ; 

 C. moniliferum rather crescent-shaped, with a 



