National Geographic : 1957 Jan
smaller clams of the southern reef, it was not rigidly fixed to the bottom. One morning when the tide was low I conducted an experiment. I asked a muscular young Queens lander, Herbert Hussey of Gordon vale, a visitor on the island, to ob tain a two-inch-thick wooden pole and then wade out with us to where the clam lay, its valves agape. Next I requested our friend to lower, rather abruptly, one end of the long pole between the clam's "jaws" and to touch the inner tissues with it. This was a "human foot" stepping into the clam. We watched carefully as Hussey carried out the instructions. Down went the pole, and in a matter of a second the valves had clamped shut. I emphasize the speed because some have reported that such clams close sluggishly and therefore constitute no undersea hazard. "Now pull out the pole," I said. The more Hussey tugged, the tighter the valves gripped. At last he was pulling so hard that he lifted the entire clam, dripping, out of the water, where it clung to the pole by the sheer strength of its bite Flashl (page 20). At du Another day on the Green Island clouds, s orchardis reef Eda and I came upon a giant Island b anemone. The creature, clinging to the side of a small pool, was a full twenty inches across, with its surface comprising a veritable forest of olive-green tentacles all writhing, swaying, expanding, and contracting like the serpents on the head of a Gorgon. As in the case of coral polyps, I knew that hundreds of tiny crustaceans and other plank ton organisms invisible to me were every moment being paralyzed by the poison cells which lined the surface of those "fingers," then devoured in the creature's central maw. Dainty Fish Live Dangerously A fish no longer than my little finger seemed to be resting there among the deadly tentacles. It was one of the loveliest I had ever seen, with three separate bands of stark white that shone like luminous paint running ver tically through its orange body. Now and then the fish would dart away from the tentacles as though in pursuit of something, then flash back, plunging into the 41 bulb Surprises a Fruit Bat Dining on Mango sk the flying foxes break camp and swirl off in dense seeking blossoms and ripe fruit. Though a plague to ts, they do not molest humans. Eyes of this Thursday at glow like a cat's in a headlight. anemone again like a child diving into a deep feather bed (page 45). How and why this fish can cavort in closest possible proximity to tentacles whose poi sonous sting will stun other small creatures that dare come close is an old and intriguing problem in marine biology. Is such a fish im mune to the anemone's poison, or is it some how able to prevent the poison cells from discharging? Who benefits from this cama raderie, the fish, the anemone, or both? I recalled the case of the Portuguese man of-war, among whose lethal tentacles another species of small fish lives in just such a fash ion.* Biologists have as yet no satisfactory explanation for these delicately balanced re lationships between coelenterates and fish. One day about dusk, as I returned from a solo collecting trip, Eda greeted me ex * See "Man-of-War Fleet Attacks Bimini," by Paul A. Zahl, NATIONAL GEOGRAPHIC MAGAZINE, February, 1952.