TWINS DOUBLE SCIENCE'S GENE RESEARCH.(Living Today)

Byline: Robert Whitaker Staff writer

One morning, art teachers Teresa Constance Eldredge and Constance Teresa Pallozzi switched jobs. No one even batted an eye.

"I was teaching elementary school at the time, and I wanted to know what the older kids (at the high school) were like," Teresa recalls, smiling at the memory. "We didn't ask. We just did it, and nobody ever knew."

Teresa Constance and Constance Teresa are identical twins, born on a farm in Wallkill, Ulster County, in 1933. They've rarely been apart since. They roomed together through the State University College at New Paltz and graduate work at the State University at Albany, shared an apartment after moving to the Capital District to teach, and, after marrying, built homes next door to each other in East Greenbush.

"The closeness we have with even our husbands isn't the same as the closeness we have with each other," admits Teresa. "What we share is from birth. Even our kids never understood our closeness."

Twinship. To those who came into the world alone, the bond twins share often is both fascinating and mysterious. "A singleton will never understand a twin," Teresa says. "It's like talking to the wind."

Indeed, while singletons (non-twins) may have brothers and sisters, and their parents, they are fundamentally - as poet Matthew Arnold put it - "in the sea of life enisled,"

separated from others by "the unplumbed, salt, estranging sea."

But twins? After sharing the womb, often they are more like double stars, linked together by an invisible filament from cradle to grave.

"It's usually the first thing I say about myself. 'I'm a twin,'" says 18-year-old Sara Siegmann, a freshman at Russell Sage College in Troy. "If I wasn't a twin, I'd be totally different."

Adds her sister Lora: "I wouldn't like it at all."

At the Minnesota Center for Twin and Adoption …