48 On the Formation and Growth of Coral Reefs and Islands. 



foundation of the sea, at a depth that cannot be measured, whilst their 

 extremities are lost in the regions of the clouds."* 



In proof of the views we are adverting to, with regard to the depth at 

 which they actually commence their growth, we have only to mention that 

 it is in some degree corroborated by the following facts : — Within the 

 lagoons, upon a calm clear day, the smallest objects may be seen at a 

 depth of one hundred feet or more;t and at these times, the bottom may 

 be observed strewed witii dead shells and broken fragments of coral ; 

 whereas, if the animals could exist at such depths, the centre of the 

 lagoons would be seen paved with these productions, and exhibiting, even 

 in a more beautiful form, the living analogues of the surrounding reefs ; 

 yet here and there, in somewhat shallower depths, we find a solitary 

 specimen, which by accident has been broken off from the reefs above, 

 growing and extending itself upwards, like a plant partially deprived of 

 light and air. 



In this manner many of the differences, which are supposed to distinguish 

 species, may be explained ; thus, if we suppose a flattened wide-spread- 

 ing fragment of madrepora prolifera, to be broken off from the upper part 

 of the reef, this fragment, if its vitality was not destroyed by its descending 

 into too great a depth, would then commence a lengthened growth, with its 

 branches ramifying like stags' horns, and forming the species called cer- 

 vicornis. 



We ought to mention that the lagoons are studded with smaller reefs in 

 all the various stages of their growth ; and in these we have the best 

 evidence of the depths at which the polypiers commence their work, as in 

 most cases their nucleus, or rather the foundation of their structure, is a 

 portion of the surrounding reef dismembered from its original situation, 

 and washed into deeper water ; upon this the polypes build their habita- 

 tions, each appearing to act independently in the creation of its own cell ; 

 while the whole seem actuated by a common instinctive principle, which 

 induces them to extend the colony upwards towards the surface of the 

 water, in the form of sugar loaves ; when the apex of the cone has reached 

 to within a few inches of the low-water level, the innate principle before 

 mentioned directs tiieir operations laterally, when, after a time, they as- 

 sume the form of a mushroom upon its pedicle. 



These clumps do not arise from a greater depth than sixteen or seven- 



* Lamoroux's views were probably derived from the accounts given by various 

 voyagers ; Flinders, for instance, who speaks of their being based at a depth of two 

 hundred fathoms or more. This idea must have arisen from the observer having 

 sounded and obtained those depths, along-side coral formations, and not taking into 

 consideration the fact of the coral being formed upon the summits of sub-marine hills. 



f In rough weather, the bottom may be observed exceeding well, by looking 

 through a tube, with one end inserted just beneath the surface, or by dropping a 

 small quantity of oil on the water. 



