66 DROPS OF WATER. 



first view from the last genus. The segments 

 are broader than long, and in many species elon- 

 gated into a process. This is of a more angular 

 form than Arthrodesmus. 8. cuspidatum (Drop I. 

 fig. 7) will serve as an example. 



Closterium is a very interesting and striking 

 genus. Many of the species are large, and all of 

 a deep green colour ; the form also is very grace- 

 ful, the two valves are elongated, narrow, curved, 

 and often of the form of a crescent, the union of 

 the two being marked in the middle by a pale 

 line, but there is no constriction there, as in the 

 former genera, and there are neither spines, nor 

 prominences of any kind. In some species there 

 are lighter green dots arranged down the length, 

 or scattered about, and in most may be perceived, 



