66 AQUATIC MICROSCOPY FOR BEGINNERS. 



ules from the particles in the streams; it has also been 

 stated that occasionally one or more of the swarming 

 granules leaves the vacuole, enters the current, and 

 journeys round the cell. These statements are cor- 

 rect. Although the occurrence seems rather uncom- 

 mon it may be the reader's good fortune, as it has been 

 the writer's, to see one or more of these intra-vacuolar 

 crystals leave their spherical dwelling place, and pass 

 into the protoplasmic stream, to be carried up and 

 , down with the currents that flow beneath the cell-wall. 

 I have seen several crystals thus escape to liberty 

 from the same vacuole, in the extremity of a Closter- 

 ium. But with, a high-power objective (the one-fifth, 

 for instance) it is not difficult to. select a granule in 

 the general stream, and follow it as the current car- 

 ries it down one side to the vacuole and again upward 

 with an ascending current to continue the round. 

 The vacuoles themselves are visible with a good low- 

 power objective, but to see distinctly the swarming 

 granules and the general cyclosis a one-fourth or one- 

 fifth is needed. 



In addition to the desmids and the diatoms, almost 

 every pond and stream contains other minute plants 

 of interest to the microscopist, called the fresh-water 

 Alg». which he probably already knows, if not by this 

 name, at least by their general appearance, for they 

 form those green masses floating like a scum on the 

 surface, or those soft green clouds attached to sticks 

 and stones and dead leaves. The Algae often have a 

 repulsive appearance as they collect in thick and heavy 

 patches, but under the microscope they reveal beauty 

 undreamed of. All those slimy, slippery green 

 streamers usually so abundant in still water during the 



