4 JOURNAL OF THE [January^ 



ence of the subject, even if we are unable to solve our problem 

 in its entirety. By way of accomplishing what we can in this 

 direction, it is necessary to begin by procuring specimens of the 

 things we propose to investigate. Fortunately they are not dififi- 

 cult to obtain. In fact, they are amongst the most plentiful of all 

 objects, though not ordinarily within the range of our unaided 

 sight. To him who has access to running brooks, quiet ponds,, 

 or the greater lakes, a range of several hundred species or varieties 

 is open. To the explorer of brackish estuaries and the deep salt 

 sea, other hundreds offer themselves. To the one who can dig 

 into the extensive deposits of their fossil remains, still other hun- 

 dreds present their interesting forms. But even to us who dwell 

 within the barren walls of a great city an unstinted supply of cer- 

 tain kinds is always close at hand, for the simplest of filters ap- 

 plied to a Croton-water faucet will, in a few minutes, furnish at 

 least a half a dozen species; and this will be our most convenient 

 source of supply. 



If we take the product of our rude filter and place dippings 

 from it under the microscope, we shall at first experience some 

 embarrassment because of the multiplicity of objects presented 

 to our view. There will be an abundance of sand and other 

 amorphous and inorganic substances, and amongst these are likely 

 to be scattered fragments of leaves and stems of exogenous 

 plants, bits of linen, cotton or woollen threads, and various other 

 articles of extraneous origin. Prominent, however, because of 

 their bright color and considerable size, will appear the long 

 jointed tubes of a few of the thread-like aquatic weeds, while 

 deep down through the film of water we shall discern two similar 

 and yet somewhat different sorts of diminutive bodies, which are 

 sure to fasten our attention by their very pretty and symmetrical 

 forms. The one kind is of a deep green color, the other of a 

 thin reddish or brownish-olive hue ; and both will exhibit some 

 differencing of their internal substance into denser and more 

 attenuated parts, with here and there open, oily-looking spots. 

 The dark green bodies appear as single capsules, narrowed, if not 

 pointed, at each end, and floating free or else as loose aggrega- 

 tions of similar flattened cells, forming either rosettes or lace-like 

 mats of various patterns. The brownish bodies will be found 

 either as narrow rods, laid side by side in long bands, or joined 



