DIATOMACE.# 193 
after successive divisions of the same kind, and 
always in the same direction, form a chain. Since 
Fic. 59.—Pinnularia viridis, a, valve view; b, girdle view; ¢, the new 
valve has foreed the girdle apart highly magnified ; d, diagram of successive 
divisions of a Diatom. (a, b, d, after Ptitzer.) (P. viridis is a fresh-water form.) 
every fresh division leads to the formation of new 
valves, the edges of which are within the girdle of 
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