A unique weekend science program for gifted children

Shallow bowls of periwinkles, each basked in a flashlight's glow, line one counter of a Fordham University science classroom. In another corner of the room , plastic salad dishes filled with lettuce, carrots, and celery host live mollusks that will presumably help themselves to a preferred vegetable.

Among the dishes is a box labeled ''Instant Ocean.'' Mixed with water, its contents produce the oceanic fluids needed to keep marine species alive.

At tables around the room, elementary school students from New York's five boroughs intently dissect magenta-flecked squid.

''Mommy, there're no feet, only arms!'' observes a boy fascinated by the squid's cartilage beak and siphon.

The class this morning will go on to conclude that periwinkles, even induced by light, emerge only slightly from their shells. They'll compare this trait with those of the land snail, which can be coaxed out of its shell and leaves a conspicuous trail.

These discoveries are part of a four-session mollusk biology unit called ''The Shell Game.'' Mollusk biology, in turn, is one theme in a lively Saturday science program for gifted children at Fordham's Lincoln Center branch.

The program is offered at two levels: 7- to 10-year-olds, and later in the day, 11- to 15-year-olds. George Tokieda, science co-chairman of Manhattan's Brearely School and former staff member at Woods Hole Oceanographic Institution on Cape Cod, teaches ''The Shell Game.'' Mr. Tokieda subtly changes his teaching approach and the materials presented in keeping with the age difference between the groups. Common to both classes, though, is a visible, audible sense of wonder for these creatures of pond and sea.

Other units of the program, which originated seven years ago at the Bank Street College of Education, have been taught by luminaries of the scientific community, including astrophysicist Robert Jastro, forensics expert Nicholas Petraco, and science journalist Gerald Jonas. Young people, and parents, are treated to units ranging from a tetrahedron kitemaking workshop that builds on the principles of aviation to an anthropological glance at ''Village Life in New Guinea.''

In May, program participants will go to the circus. Peggy Williams of the Ringling Bros. and Barnum & Bailey Circus, who has managed to bridge careers in education and clowning, will give students an inside glimpse of ''The Science of the Circus'' (animal behavior, the physics of aerial acts, the science of color as used in circus lighting, the psychology of clowning).

The Fordham program's imaginative outlook reflects the vision of its initiator, Sylvia Hecht. Mrs. Hecht, an accomplished concert pianist since age 8 and a veteran in the field of educating the gifted, suggests that learning is refreshed for gifted students - and all students - when ''basic'' subjects are treated with artistry.

For some of these students, the program is a natural extension of a way of life. Jeffrey Gladstone of the Sheepshead Bay neighborhood, for instance, is the son of a scientist who graduated from Fordham. Twelve-year-old Matthew Messinger of Queens wrote a prizewinning essay last year that won a National Geographic safari to Kenya. Matthew, who hopes to become a neurosurgeon, says his favorite project within this program was comparing electronic wiring with the human nervous system. His mother calls the program ''superior, because it allows their curiosity to come out.''

For other program students, this is a whole new world. Two underprivileged students, for example, are able to take part because of scholarships and the commitment of a Brooklyn public school teacher willing to provide weekly encouragement and transportation.

The program receives financial support from the New York City public schools, Science Digest, and Fordham University itself. Participants are chosen by public school assistant principals and science department chairmen. The same group of educators selects scholarship recipients.

To close today's sessions, George Tokieda gathers students in a circle to scrutinize a fish. He then describes differences between periwinkles on Long Island's bay side and those indigenous to the ocean side. Rocks on the bay side are rounded by the patterns of water flow, he explains, and the periwinkles are rounded correspondingly. Ocean-side periwinkles, because of the ocean's action, are more jagged.

As they leave today, students are given a packet containing a pond snail and an aquatic plant. If they add spring water to the container, Tokieda informs them, they will have a pocket-size natural environment in the thick of the metropolis.

''My son gave up being on a soccer team so he could do this,'' says Ilario Pantano's mother. ''They're here because they love it.''