128 A NATURALIST IN CELEBES ch. vi 



it is just three feet across— stand up a number of blunt 

 processes or tubercles an inch or two in length and half 

 an inch in diameter, bearing the youngest polypes. The 

 whole coral is dark, dull, orange green, but the growing 

 points and polypes are distinguished by a brighter yellow 

 colour. 



A little further on there is a dirty white lump of 

 Millepora plicata in the form of four leaves or plates with 

 'their upper edges slightly turned over towards the deeper 

 water. I wonder if the delicate hydroid polypes are ex- 

 panded there in their natural position, so planting my feet 

 firmly on the ground and handing Manuel my hat, I take a 

 deep breath and plunge my head and shoulders into the 

 water to see. But they are not, and my trouble and dis- 

 comfort is for nought. A few paces further on another 

 madrepore of a different species attracts my attention. It 

 is of a different shape to the last, and is of a deeper reddish- 

 brown colour, the growing points being delicate violet or 

 purple. 



All this time I have been wading along the outer 

 edge of the reef among the growing corals, but I never 

 feel satisfied unless I examine at the same time the fauna 

 of the inside of the reef ; i.e. that part of the reef which 

 at the lowest spring-tides is left partially or completely 

 uncovered. This region is usually strikingly different to 

 the outer edge, which is never uncovered, and is very gene- 

 rally the best locality for Tubiporas and Clavularias, that 

 in some places literally carpet the ground. When the 

 polypes are fully expanded it is not easy to distinguish the 

 Tubiporas from the Clavularias. All that the naturalist 

 sees of them is a waving mass of deep-brown polypes with 

 pinnate tentacles so closely situated to one another that it 

 is impossible to see anything between them. The lumps 

 of Tubipora are sometimes a foot or more in breadth across 



