THE SOLUTION THEORY. 
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minute organisms which inhabit the upper stratum of the 
ocean water seems at first considerable, but when we 
estimate its thickness in a given area, this proves to be 
extremely small. Hence, unless we assign a very brief 
existence to each individual, and thus suppose a heavy rain 
of shells on the ocean floor, the foundation for the future reef 
will rise but slowly, and its initiation, in the case of those 
which now exist, must be carried back to a rather remote 
epoch. Here, again, we may inquire whether a cause, which 
must not be wholly overlooked, has not, through an error 
in mental perspective, been brought into undue prominence. 
3. The solution theory, which indeed by no means 
meets with universal acceptance among Mr. Darwin’s 
critics, appears to me beset with considerable difficulties. 
The solubility of carbonate of lime in ocean-water cannot 
of course be denied ; but is there satisfactory evidence that 
this is a factor of primary importance to the case of a 
coral reef ? The apparently rapid solution of calcareous 
organisms at great depths has but little bearing on what 
occurs at small depths, and the good preservation of the 
‘ globigerina ooze ’ down to depths of some 2,000 fathoms, in 
itself indicates that solution to any important amount takes 
place under very exceptional conditions. The rottenness 
frequently noted in dead coral is mainly due to the decom- 
position of the animal tissues with which the mineral 
constituent is incorporated : thus the process is one of 
disintegration more than of solution. The dead coral is 
no doubt to some extent dissolved, but it mainly forms a 
sand or mud. This of course, in some cases, will be swept 
out by currents into the open ocean, and thus the coral 
will be removed from its place of growth, but it may well 
be doubted whether this substitute for a true solution will 
be for long a factor of prime importance in the genesis 
of a lagoon. There is moreover some evidence directly 
opposed to the theory of solution at a moderate depth, as, for 
