40 



PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



The wide southeast reef-flat of Maer Island is peculiar in that the 

 lithothamnion ridge forms a dam which prevents the water from escaping at 

 low tide thus impounding a huge, shallow lake having a minimum depth of 

 from 4 to i6 inches (see table i) at low tide, while at high tide the water is 

 everywhere between 7 and 8 feet deep. 



One sees that Seriatopora hystrix, which is the dominant coral of the 

 middle zone of the reef-flat, is cut ofl^ squarely at low-tide level and indeed 

 there are few corals excepting Acropora which project more than 2 to 3 inches 

 above the level of the water at low tide. 



EXPERIMENTS UPON DRYING CORALS. 



Experiments upon drying various corals from this reef confirm Vaughan's 

 conclusions' based on his experiments upon the Florida corals, that the forms 



Table 12. 



with spongy skeletons, provided their bases remain immersed, can draw up 

 water by capillary attraction and thus retain their internal moisture even 

 though exposed for an hour or more to the sun's rays at midday. Thus such 

 cavernated forms (as Acropora and Montipora) and to a more limited degree 



'Report of T. Wayland Vaughan, Carnegie Inst. Wash. Year Book No. 11, p. 161, 1912. 

 -This species can survive one hour in the sun with the base immersed in sea-water if the maximum temp- 

 erature is not more than 29.4° and the humidity is about 66.5 per cent, the wet bulb being 24.2° to 25.2° C. 



