146 A NATURALIST IN CELEBES ch. vi 



argument I adopt. The roots of the mangrove trees form 

 a large natural breakwater, which retains the soil brought 

 down from the mountain-slopes and the sand washed up by 

 the tides. In this way the floor of the mangrove swamp is 

 gradually being raised to form the shore platform where 

 ordinary forest trees supplant the mangroves. If there 

 had been no mangrove swamps in these regions I believe 

 there would be no shore platforms, and the coral reef, instead 

 of being only a hundred or two hundred yards from the 

 shore, would be a mile or two in many places, and could 

 then be called a barrier reef. On the island of Talisse 

 itself we have not many good examples of this, but at the 

 southern cape opposite Tindela Straits, the reef is at least 

 three-quarters of a mile from the nearest rising ground, and 

 on many places on the west coast it must be over half a mile 

 from it. On the northern coast of the peninsula there are 

 better examples. Nearly the whole way from Cape Papal- 

 empungen to Cape Piso there is a broad shore platform, in 

 many places several miles across, and a similar condition 

 may be observed along the shore from Manado to Tana- 

 wangko. Here then, I believe, if there had not been a 

 mangrove swamp to form new land upon the shore as the 

 coral reefs extended seawards, we should have had a barrier 

 reef with perhaps a deep lagoon. 



Before leaving the fauna of the coral reefs of Talisse, 

 two points in connection with the vital economy of the 

 polypes claim our attention. In the first place, is it possi- 

 ble to state with any degree of certainty what the corals 

 feed upon ? It has been usually assumed that their food 

 consists almost exclusively of small free-swimming pelagic 

 animals which they catch with their tentacles as the tides 

 flow over them. There can be no doubt that, broadly 

 speaking, this assumption is true. The batteries of stinging 

 cells — nematocystB — found upon their tentacles must be for 



