It turns out that jellyfish may hold the secret of eternal youth. I had thought it was mirrors. Each morning, when I look in the mirror, I see . . . me. The face staring back is the same one I have encountered for years. The daily changes are imperceptible and, of course, mirrors don’t lie. Aging pretty well, I smugly think.

Actually, mirrors do lie. But passport photos don’t, as I discovered yesterday when I got pictures for my trip next year to Burma and Vietnam. When the clerk handed me the 2”x2” portraits, I looked into an almost unrecognizable face – with the lines of an old man, yellowing teeth and gray hair that my passport swears is brown. This face looked nothing like the one I hard earlier seen in the mirror. No wonder strangers call me “sir.”

“You know what the Brits say,” said my friend David, who had had a similar experience, “’When you resemble your passport photograph, you are in need of the journey.’”

Enter Turritopsis dohrnii, the “immortal jellyfish” featured in the Times Magazine. This tiny invertebrate lives a circular life: it grows and then ages in reverse, returning to its earliest stage of life, from which it sets off again.  Jellyfish are more genetically similar to us than we might want to admit, which bodes well for stem-cell research. But the real excitement is the immortality bit.

Shin Kubota, a Japanese scientist who has studied Turritopsis for 40 years, believes we can learn its secret. But “before we achieve immortality,” he warns, “we must evolve first. The heart is not good.”