Nature Bulletin No. 259-A   March 4, 1967
Forest Preserve District of Cook County
Richard B. Ogilvie, President
Roland F. Eisenbeis, Supt. of Conservation

****:LIFE IN A DROP OF WATER

A drop of pond water appears clear and lifeless to the naked eye but 
within it are many queer creatures that can only be seen when viewed 
through a high-powered microscope. The first simple microscopes, 
magnifying ten times or less, were made by Dutch spectacle-makers in 
the 16th century. These aroused a great deal of wonder and it was 
considered particularly fascinating to watch live fleas with them. Thus 
they became known as "flea glasses". By 1674, the self-taught Dutch 
naturalist and lens-grinder, Leeuwenhoek, had made microscopes 
giving magnifications up to 270-power and had begun to tell about the 
multitude of very small living things he saw in water. A whole new 
world of life was revealed for the first time.

Since then, thousands of species of microscopic water plants and 
animals have been described and given scientific names. Common 
English names are rare. They can multiply at an enormous rate and are 
the most abundant living things in both fresh and salt water. A single 
quart of water may have more individuals in it than there are people in 
the world.

One of the better known creatures, one that often swarms in puddles 
and ponds, is the Paramecium or Slipper Animalcule which is barely 
visible to the naked eye. Seen under a microscope, its body is a single 
cell enclosed in an oblong flexible envelope covered by thousands of 
short hair-like "cilia" that actively row the animal about. Near the front 
end is a broad deep groove with a mouth opening at the bottom. Into 
this opening the cilia in the groove sweep bacteria, algae and other 
small life on which it feeds. The Paramecium multiplies by merely 
pinching itself into two parts. The front half grows a new back half, and 
the original back half grows a new front half with a groove and mouth 
opening. There is nothing left which can be called a parent. Neither are 
t here males or females.

Another microscopic one-celled animal, the Ameba, looks like a bit of 
grayish jelly that seems to slowly melt and flow over submerged water 
plants, dead leaves and mud. It feeds by merely flowing around smaller 
organisms and, like the Paramecium, multiplies by merely dividing. 
Another, the Vorticella, forms colonies on underwater surfaces. Each 
animal is a bell-shaped "head" attached to a long stalk that jerks back 
like a coil spring when danger threatens. It gathers food with its ring of 
cilia around the lip of the bell. Noctiluca, a microscopic animal that 
swarms in sea water, produces a phosphorescent glow when disturbed 
by a breaking wave or a passing ship.

Microscopic water plants, like larger plants, contain green coloring 
matter, or chlorophyll, by which they manufacture their own food in 
sunlight. Single-celled plants -- Diatoms, Desmids and certain other 
algae which multiply by dividing like the Paramecium -- numbering into 
billions of individuals, produce the golden brown masses that cover the 
beds of streams and aquatic weeds, or the film of green "bloom" or 
"scum" on the surface of lakes and ponds. In water supply reservoirs, 
certain ones give a fishy, a bitter, or a cucumber taste to the water. In 
other kinds of algae, such as Spirogyra, the cells divide but remain 
attached to form long threads which, in masses, look and feel like 
slippery green hair.

There are also strange creatures that swim with long whip-like 
"flagella" and eat like animals, but which have green chlorophyll and 
behave like plants in Some ways. They straddle the boundary between 
the plant and animal kingdoms.

Such microscopic organisms, called "plankton", are the staff of life -- 
basic food -- for all animals that live in water.