The Water Nets 



123 



cells of the old colonies. A new complete miniature 

 net is formed within a single cell; and after its escape 

 from the old cell wall, it grows, not by further division, 

 but by increase in size of its constituent cells. 



Water net is rather local and sporadic in occurrence, 

 but it sometimes develops in quantities sufficient to fill 

 the waters of pools and small ponds. 



Fig. 44. Pediastrum: Several species from the plancton of 



Cayuga Lake. 



Pediastrum is a closely related genus containing a 

 number of beautiful species, some of which are common 

 and widespread. The cells of a Pediastrum colony are 

 arranged in a roundish flat disc, and those of the outer- 

 most row are usually prolonged into radiating points. 

 Several species are shown in figure 44. In the open- 



