CH. VI MARINE FAUNA OF TALI88E SHORE 8 147 



the purpose of paralysing or killing small organisms which 

 come in contact with them, and from the analogy of our 

 own sea-anemones we are justified in assuming that; 

 organisms thus killed are conveyed to the mouth by the 

 tentacles and swallowed. On the other hand, I have care- 

 fully examined sections of reef polypes of various kinds 

 and, with the exception of Millepora, I have not yet been 

 able to discover any remnants of animal food in the 

 body, cavity, or throat of any of them, and moreover two 

 authorities I have spoken to on this subject, both of whom 

 have examined far greater numbers of these forms than 

 I have, assure me that their experience in this respect 

 coincides with mine. It seems probable therefore that 

 their meals of animal food, of a size large enough to 

 be distinguished with the microscope, are few and far 

 between. I do not think we are justified in assuming 

 that the corals are dependent entirely upon the small 

 Crustacea and the like which are brought to them by the 

 tides. The currents of water which are constantly kept 

 up in and around the throat by the action of thousands of 

 minute cilia must bring with them numerous extremely 

 minute organisms upon which the corals may feed. But 

 food which is brought to the polypes by this means must be 

 of a very heterogeneous description and mixed with parti- 

 cles of sediment floating in the water. Now, in the water 

 which flows over the reef there is in many places in sus- 

 pension the scourings of the mangrove swamps. Fruits, 

 leaves, and wood undergoing decomposition and disintegra- 

 tion fill the water with shreds of vegetable matter which 

 gradually sink to the bottom. Some of these must find 

 their way into the throats of the thousands of little polypes 

 on the coral reefs. Particles of vegetable fibre are fre- 

 quently found on the mesenterial filaments of the Alcyo- 

 narians I have examined, and it may be they also occur in 



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