110 THE MADREPORE. 



pieces of rock, and all displayed their beautiful strac- 

 ture without any reserve. 



Just eight weeks have now elapsed since I took the 

 specimens above-mentioned ; and I have added two 

 more which I found at Hele, adhering to the perpen- 

 dicular side of a narrow, but deep I'ock-basin. They 

 are all alive and in excellent condition, with the ex- 

 ception of one or two that I selected to experiment 

 on. I shall proceed to describe these interesting and 

 beautiful pets. 



Doubtless you are familiar with the stony skeleton 

 of our Madrepore, as it appears in museums. It con- 

 sists of a number of thin calcareous plates standing 

 up edgewise, and arranged in a radiating manner 

 around a hollow centre. The upper edges of these 

 plates are rounded in their outline, and are free, that 

 is, not in contact with each other ; but a little below 

 the outer margin, their individuality is lost by the 

 deposition of rough calcareous matter, mingled and 

 overlaid with dirty floccose extraneous substances ; so 

 that only the general form is discernible on the out- 

 side, except at the very summit. This general form 

 is more or less cylindrical, commonly however a little, 

 and sometimes considerably wider at the top than just 

 above the bottom. The base itself is a flat expansion, 

 or rather a low cone, of which the breadth varies 

 greatly in different specimens. 



The plates are not all of the same size. There are 

 commonly about fifteen principal ones, which are 

 higher than the rest, and project more into the cen- 

 tral cavity. Between each of these and the next, are 



