OF ALL OF THE students in Mrs. Nickle's first-grade class, none had a more refined appreciation of pollywogs than I. Our teacher kept the school aquarium full of local pond life, and the class delighted in observing the steady metamorphosis of tadpoles to frogs. As the official pollywog monitor (a job I begged for and got, much to my mother's horror), I was responsible for replacing the amphibians that made the leap. I still remember those sunny spring afternoons when, sporting my oversized safari hat and carting a satchel brimming over with empty mayonnaise jars, I trekked to our nearby pond intent on bagging a "gazillion" tadpoles.

For me, and I suspect for most amateur naturalists, ponds remain a treasure trove of wonders. There are four spheres of life around a country pond: the water itself, the mud beneath the water, the air above it and the soil around it. A myriad of creatures have evolved to exploit these special habitats. Water snails stealthily patrol the bottom. Toads hunt insects and their own smaller brethren in nightly melees along the banks. Dragonflies skim the surface to deposit their payloads of eggs. If you're lucky, you'll spy minnows, newts and diving beetles taking refuge among the aquatic plants.

Most nature books wax verbose on the habits of local species but are disappointingly terse in the how-to details of specimen collection and preservation. The shining exception to this gloomy rule is Gerald Durrell's marvelous practical guide, The Amateur Naturalist (David McKay Company, Random House, 1989, $25, ISBN 0-679-72837-6). This book once so invigorated my excitement for ecology that I almost abandoned my graduate studies in physics to become a professional naturalist. Most collection methods I've developed, including those described here, are merely refinements on techniques I first learned in the pages of The Amateur Naturalist. Armed with these methods and a good field guide, an ambitious amateur can delight in and advance the study of pond ecology.

(City dwellers, take heart. Although not as diverse as the perennial country pond, any standing pool of water will, if left alone for a month, become home to a surprising number of living things, such as algae and water insects. Natural streams from heavy rains often bubble up in the heart of urban sprawl, and pools along storm drains are regularly replenished with runoff. Perhaps you can let a wading pool go native. And there are almost certainly ponds, lakes and reservoirs within an easy drive.)

Like moths to flame, some inhabitants of the murky depths are attracted to light. You can catch many of these critters using the light-baited trap shown above. A flashlight is safely housed inside a sealed glass jar and placed within a simple trap. The funnel opening guides creatures in. Once inside, they have little chance of finding their way out again.

I've used wastebaskets and large-diameter aluminum pipes for the trap's main chamber. You can fashion the funnel out of an old white T-shirt and coat-hanger wire. Situate the flashlight to illuminate the cloth opening. Put the trap in the pond before sunset and hoist it up later that evening to examine your catch.

As a variation, try building a circuit that flashes the light. Plans appear in Getting Started in Electronics, by Forrest M. Mims III (Radio Shack, $4.99). I've always wanted to build such a circuit to see which species come calling when lured by a pulsating invitation, but I haven't managed to get toit. You can also experiment with different pulse frequencies. Let me know what you find.

A homemade grappling hook is invaluable for snagging aquatic plants. The tines can be fashioned from coat-hanger wire. Use insulated electrical wire to lash the tines to the end of some nylon cord. Next, saturate the electrical-wire wrappings with a generous layer of epoxy and let it set. Wrap the assembly with duct tape and slide a narrow piece of plastic pipe over it for protection. Finally, seal out debris by filling the pipe with epoxy. Deploy the grapple by swinging it around your head and letting it fly into a shallow of water plants. Then pull the plants toward you. You might also find some interesting guests on the fronds and stems.

To examine bottom-dwelling life, you'll need a dredge net. Purchase 54 inches of three-quarter-inch diameter plastic polyvinyl chloride (PVC) pipe from a plumbing supplier and cut it into three 18-inchlengths. Next, you'll need nylon fish netting. Some fabric stores and bait-and-tackle shops carry it(look under "Netting" in the Yellow Pages). The size of the mesh is not critical. I buy three-quarter-inch web (diamond-shaped netting) for 32 cents per square foot. It comes in bolts 20 feet wide by 300 feet long, although you will need only a 60- by 60-inch square. Retailers are usually happy to trim it. From the square, cut out an equilateral triangle 60 inches to each side.

Using an old paintbrush, liberally coat one of the PVC pipes with one-hour epoxy. Place the pipe at one base of the triangular netting and carefully draw in the netting along both sides, leaving clear one inch of pipe at either end. Roll the netting around the pipe twice. Stitch the netting in place with a couple of twist ties so the pipe won't unroll. Then hang the pipe over some old newspapers and pour on more of the one-hour epoxy, thoroughly covering the pipe.

Split lengthwise three 14-inch sections of garden hose. These protect the net while it is being dragged. Slip one of the split lengths of hose over the pipe. Hose clamps will clasp the assembly tight while the epoxy sets, but they are a pain to attach. I prefer to smother the assembly under plastic trash bags filled with sand. Repeat the same procedure with the two other pipes, rolling them up on the other sides of the triangular net. You will end up with a dredge net about 28 inches deep and 18 inches to aside. Next, fill one of the pipes with sand and cap the ends with cotton wadding soaked in epoxy. This weighted side drags along the bottom.

Now you need to link the pipes together to form a rigid frame. From a plumbing supply store, purchase a short length of one-half-inch flexible (L soft) copper tubing and six unthreaded bell reducers. They are fittings that join two different size pipes-in this case, they should connect three-quarter-inch pipe to one-half-inch pipe. Cut a two-and-a-half-inch section off the copper tubing and thread two bell reducers over the ends of the cut piece so the fittings are separated by about a half inch. Epoxy the bell reducers into place with low-viscosity aluminized epoxy-available from Devconin Danvers, Mass.; call (508) 777-1100 for the nearest distributor. Before gluing, be sure to roughen the ends of the tube and the inside surfaces of the bell reducers with coarse sandpaper.

Once secured, bend the tubing to form a 60-degree angle. You can make the bent tube rigid by filling it completely with epoxy and letting it set. Use a knife to score the ends of two adjacent sections of pipe and epoxy the bell reducers over the ends (again, use aluminized epoxy). Repeat the entire procedure twice to finish the rest of the frame. Paint the copper tubings to prevent corrosion.

The dragline completes the assembly. Tie eight inches of nylon cord to each point where a bell reducer meets a PVC pipe, then tie the opposite ends to form three pairs. Melt these ends together with a soldering iron. Tie these three points with nylon cord so they come together about two and a half feet in front of the assembly. Finally, tie this point off to at least 100 feet of nylon line. Make sure to adjust the cords so that the opening of the net tips backward about 10 degrees when dragged.

The soil around a pond is host to millions of tiny roundworms called nematodes. Only about one millimeter long, these nearly microscopic organisms are second only to protozoans as the most abundant creatures on the earth. A cubic meter of soil can harbor 12 million of them. A vital part of pond ecology, they can be especially interesting to study. Just make sure you observe strict sanitary practices-ingested, a few species are parasitic. Wear rubber gloves and wash thoroughly after fieldtrips.

To collect nematodes, slip a small piece of rubber surgical tubing over the end of a funnel and clamp the opening shut with a clothespin. Place muddy soil into the funnel, pouring in enough pond water so that some water stands free on the soil surface. The nematodes will sink into the funnel's neck. Wait five minutes before disgorging your booty into a container with a few gentle shakes and a momentary release of the clothespin.

A similar technique enables you to collect insects from most soils. Carpet the bottom of a glass jar with blotting paper. Insert a funnel, neck downward, into the jar's mouth and loosely fill the funnel with collected soil. Place a bright, incandescent desk lamp directly over the soil. To escape the light and heat, the insects will tunnel deeper into the soil until they fall onto the blotting paper. Try conducting an insect and nematode census around a pond at different times of the year.

There are a few rules that all naturalists must follow. Never enter private property without permission. Never disturb protected or endangered marshlands. Never collect specimens in excess of your immediate needs. Clear your activities with whatever authority may be responsible for the area. If you study more than one pond, wash your equipment thoroughly with soap and water to prevent transplanting microscopic organisms. Remember, violating these rules will not only make things hard on you. Landowners and park authorities may begin forbidding access to all amateur naturalists, even those whose only wish is to study the ecology responsibly.

For more information about amateur science projects, check the Society for Amateur Scientists' World Wide Web site.

The Society for Amateur Scientists (SAS) is a nonprofit research and educational organization dedicated to helping people enrich their lives by following their passion to take part in scientific adventures of all kinds.