Page:Popular Science Monthly Volume 85.djvu/221

Rh wins in this strife for place in the region 1,000 feet from shore. It is, however, very sensitive to high temperature, and the warm shallows close to shore are fatal to it so it can not survive within 550 feet of the beach. Also, being very slender, it can not survive the rush of the breakers and, thus it disappears about 1,670 feet out from shore where the surges shatter its fragile stems. Delicate and sensitive to high temperature, to silting, and to agitated water as it is, however, if conditions be ideal for its existence, it thrives so well that all other corals, even those that can live anywhere over the reef-flat, must give way to it.

The amount of food required to support the vast coral population of this reef-flat must be very great, especially, as Dr. Vaughan discovered, corals are strictly carnivorous and will not even attempt to capture plants. The minute floating animal life of the ocean is therefore the chief source of food for corals. Moreover, Dr. Vaughan showed that it is possible at a glance to tell the difference between a fat-looking, well fed coral and the thin, drawn appearance of a starved one. The corals of the southeast reef of Maër Island, however, all seem to be well fed, and thus it appears that the question of food has little or nothing to do with their struggle for existence.

There are, however, no large heads upon this reef, only a vast array of small ones.

Now the Murray Islands are in a fortunate region which is never visited by hurricanes, and thus the corals grow on for ages undisturbed by severe storms. Along the entire southeast beach only two small coral heads were found tossed ashore by the waves, a striking fact in contrast with the great heaps of dead coral ten feet high, found strewn along the shores of the Paumotos Islands where severe hurricanes occur.

 Pocillopora damicornis. The fragile specimen on the right grew in the calm waters of the reef flat. The rigid one on the left grew in a tide pool among the breakers. Murray Islands, Torres Straits.