134 A NATURALIST IN CELEBES ch. vi 



on the coral reef some polypes seem to be always expanded, 

 at low water, and others are always retracted. 



Passing on then from the pier towards the southern 

 cape of Talisse, noticing how wonderfully the reef changes 

 in appearance and in vigour in different localities, I come 

 at last to a great prize in the rare and beautiful Heliopora 

 ccerulea. Coral reef work has many personal discomforts 

 and intellectual disappointments, but this can be said in 

 its favour, that when a prize is found it is usually found in 

 great abundance. Nature does not reward the naturalist 

 with a little tiny specimen that must be labelled carefully 

 and put away in a pill-box in a cabinet, but provides him 

 with a sufficient quantity to make a cartload if he wishes it. 

 I had been hunting everywhere for Heliopora, and should 

 have been thankful for a smaller piece, but here at last I 

 come across a mass that it would take twenty strong men 

 to lift and carry away. Fortunately, there are several 

 smaller masses in the immediate vicinity, and I am conse- 

 quently able to take away with me sufficient for my purpose 

 without calling in the aid of the coolies from the plantation. 



Heliopora is in many respects one of the most interest- 

 ing corals of the reefs, for it is as it were a representative of 

 prehistoric times, a survival of a generation that has long 

 since passed away. Heliopora itself did not appear until 

 Eocene times, but its allies, Heliolites, Plasmopora, Propora, 

 Thecia and others, together with Syringopora, Halysites and 

 others that were probably allied to Tubipora, were the main 

 factors of the coral reefs of Silurian and Devonian times. 

 If a naturalist could have walked along those prehistoric 

 shores he would have found scarcely a single Zoantharian 

 coral, the majority of forms being Alcyonarian in structure 

 allied to the modern Tubipora and Heliopora. The intro- 

 duction of the Zoantharia at the close of the Devonian period 

 caused a rapid decrease in the stony Alcyonaria, until at 



