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We saw that there is evidence of a struggle for existence between the various kinds of corals, and according to Darwin's theory, we would expect this to have improved the corals. The Australian forms must withstand a very high temperature during the calm, hot days of the "northwest" season, while those of Florida must suffer annually from cold "northers." Yet, our experiments show that the Australian corals are quite as sensitive to high temperature as are those of Florida, and conversely the Florida corals can not withstand cold any better than can those of tropical Australia. In other words, natural selection has not improved the heat-resisting or cold-withstanding powers of the corals and yet temperature is a factor of primary importance in determining the life or death of reef corals. Of late years we have been steadily losing respect for the efficacy of natural selection as a means of developing morphological or physiological adjustments.

We must conclude that "corals are corals," and their behavior is essentially alike both in Florida and in Australia.