The glacial influence, when the corals were killed by the cool water. Therefore the Caribbean coral reefs are situated in the midst of the coastal banks and they are young in comparison to the coral reefs of the Indo-Pacific. In connection with this we have to see the following facts:

1. The number of species of reef building corals is only small in the West Indies, but high in the Indo-Pacific.

2. In the reefs of the Caribbean Region the vertical reef walls are occupied by a small number of coral species only. In the reefs off the East African Coast it is personally observed that many different species can settle on such localities.

3. In the West Indies there are no fishes with such a high affinity to corals, that they cannot live without them. On the contrary in the Indo-Pacific, fishes such as Dascyllus live between branching corals.

Thus, bolides the greater species diversity among corals, the fishes living between corals in the Indo-Pacific have had a lot of time for their evolution. In the short time of its existence, such an evolution and specific adaptation was not possible for the corals or the fishes of the West Indies. Other differences are the day and night activity and the resistance against water movements of the Indo-Pacific corals in contradictory to that of the West Indies. All corals are sensitive to fresh water, but rainfall and little ephemeral coastal rivers have nearly no action in this case in the West Indies.