Ii6 



Aquatic Organisms 



Desmids — This is a group of singtilarly beautiftil 

 unicelMar fresh-water algae. Desmids are, as a rule, 

 of a refreshing green color, and their symmetry of form 

 and delicacy of sculpturing are so beautiful that they 

 have always been in favor with microscopists. So 



Fig. 38. A good slide-mount from a Closterium culture 

 as it appears under a pocket lens. Two species. 



numerous are they that their treatment has of late been 

 relegated to special works. Here we can give only a 

 few words concerning them, with illustrations of some 

 of the commoner forms. 



Desmids may be recognized by the presence of a clear 

 band across the middle of each cell, (often emphasized 

 by a corresponding median constriction) dividing it 

 symmetrically into two semicells. Superficially they 

 appear bicellular (especially in such forms as Cylindro- 



