4° 



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 16 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 off 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 1 based on his experiments upon the Florida corals, that the forms 



Species. 



Pocillopora bulbosa 



Seriatopora hystrix 



Acropora pulchra and A. 



hebes. 

 Goniastrea pectinata 



Goniopora tenuidens 



Cceloseris mayeri Vaugban 

 Porites haddoni Vaughan. . 



Montipora ramosa 



Table 12. 



Basal part of stalk im- 

 mersed in sea-water. 

 Upper part of coral ex- 

 posed to sun's rays from 



1Q h jjm t0 n h jjm a m 



At io h 15™ a.m. Dry bulb 



29. 2°, wet bulb 24.2 . 



Humidity 72 p. ct. 

 At u h I5 m a. m. Dry bulb 



31. 5 , wet bulb 26.1°. 



Humidity 73.5 p. ct. 



Killed 



Killed 2 



Survived without appar- 

 ent injury. 

 Survived without injury . . 



Survived without injury. . 



Survived 



Corals placed on a dry bare 

 rock close by side of the 

 other corals. All other 

 conditions the same in both 

 experiments, excepting 

 that in this case the bases 

 of the corals were not im- 

 mersed in sea-water, the 

 entire stalk being dry. 



Temperature and humidity 

 the same as in preceding 

 column. 



Killed . 

 Killed . 

 Killed . 



The upper parts of the 

 coral were killed. Basal 

 half above the sea-water 

 survived. 



Survived without apparent 



injury. 

 Survived without apparent 



injury. 

 Survived 



Killed . 



Basal part im- 

 mersed in sea- 

 water, upper 

 parts dried in 

 sun for i h 30 m . 



Dry bulb 



3°-35°- 

 Wet bulb 



27.4-. 



Humidity 

 p. ct. 



83.5 



Survived with- 

 out apparent 

 injury. 



Coral wholly 

 dried in the 

 sun i h 30 m . 



Dry bulb 



3°-35°- 

 Wet bulb 



27.4 . 

 Humidity 83.5 



p. ct. 



The coral 

 barely sur- 

 vived, most 

 parts of it 

 being killed. 



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 Monti pora) and to a more limited degree 



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

 2This 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. 



