FRESH-WATER ALG&. 258 
they lie at the bottom of the ditch or pond are 
rarely worth carrying home. 
But the most extraordinary of all the members 
of this numerous and highly varied family of 
plants are the Diatoms or Brittle-worts, which 
form a wonderful microcosm of their own. It is 
but a few years, comparatively speaking, since 
the microscope has drawn aside the veil which 
hid them from our view; but our knowledge of 
them, thanks to the all-absorbing attention with 
which scientific men have regarded them, is 
already remarkably extensive and accurate. 
Though these curious vegetable atoms occupy 
the lowest place in the scale of vegetation, they 
are, nevertheless, intensely interesting and sugges- 
tive of marvellous thought. They constitute an 
immense family, the individuals of which are 
numerous beyond the sands of the sea-shore or 
the stars of heaven ; ay, even beyond the wildest 
dreams of the Pantheist. They cannot be 
reckoned by millions simply, but by hundreds 
of thousands of millions. There is hardly a spot 
on the surface of the land, or in the depths of the 
ocean, where some species or other of them may 
not be found either in a dead or living state. 
They inhabit streams, ditches, and stagnant 
pools; they clothe the leaves and fringe the 
stalks of sea-weeds; and they are found in 
