148 ME. A. E. FIXCKH. 



but a stay of often only a few hours at one particular island did not allow of minute 

 examination. 



To future investigators into the question of Lifhoth amnion growth it might be 

 suggested that attempts should be made to fasten down on to flat surfaces of living 

 Li thoth amnion fairly thick glass plates with holes of varying sizes. It will })e found 

 that the Lif/iof.hamniov immediately in contact with the glass will perish, while it 

 will continue to grow upwards in the holes. So that if the thickness of the plates 

 is given, the growth might be estimated after a number of years. The plates might 

 be fastened down to the reef rock by means of short glass legs cast in one piece with 

 the glass plate. 



(7) Expei'nnents On: — (A) Exposure of Coral and Lithothamnion to the San. (B) 

 Amount of Carbon Dioxide in Lagoon and Ocean Water. (C) Evolution of 

 Gases by Coral. (D) Observations on the Temperatures of Water. 



(A.) The experiments in connection with the amount of exposure to the sun's rays 

 which coral and Lithothamnion are capable of enduring were carried out systematically 

 only in the case of Porites limosa (the common species of the lagoon platform), 

 Pocillopora verrucosa and P. grandis of the ocean platforms and of the lichenous 

 lAthothamnion . 



Of these the Porites alone were able to withstand exposure beyond a very limited 

 amount of time. They were found to be unaffected l)y an exposure of as much as 

 twelve hours, by which time the coral seemed perfectly dried up, yet on replacing it in 

 water the polyps revived and continued to live. All the other forms were dead after 

 less than two liours exposure, immediately after they had become dried up externally. 

 Death was indicated in the case of the coral by the shedding of the gelatinous coating, 

 in the case of the UtJioth amnion by the disappearance of the pink colour. Certain 

 specimens of /-*. verrucosa were exposed in their upper parts only, while the main 

 stem was still immersed. The result was that they were destroyed exactly down to 

 the water line. 



The results of these experiments agreed with inference from general observation, 

 that the Porites alone were able to survive exposure to the sun. This exposure took 

 place at low-water spring tide in calm situations where the waves did not wash over 

 them. Other corals were foimd above the low-water spring tide only in situations 

 where they were washed by successive waves. The external gelatinous coating of the 

 Porites seems much thinner than that of other corals, a circumstance which may play 

 some part in their power of resistance to the sun and air. During these experiments 

 it was evident how very necessary a constant supply of fresh sea- water is to tlie coral. 

 Specimens were kept In enamelled basins for purposes of observation, but it was found 

 invariably that, even when the water was changed every three to five hours, they did 

 not survive the second da v. 



