MALADIVE AND KEELING ATOLLS. 305 
by many observations, is much at variance with the old 
accepted saying that corals grow best where the breakers 
are the heaviest. It appeared to me that heavy breakers 
are not favourable to coral growth, because of the quantity 
of shingle which they dash against the soft-bodied polyps. 
Borne massive forms might withstand the force of breakers 
and violent currents if the polyps could be sufficiently 
protected from the shingle, but the branching madrepores 
are soon broken off and swept away, and even the more 
massive maandrina soon follows, for whilst the surface of 
the colony grows the base is dead, is soon riddled by boring 
sponges, serpulae, &c., and is no longer able to bear the 
strain put upon it. The great mass then breaks off and is 
rolled along the reef, pounding other corals in its course.’ 
Still, as a rule, the outward portions of the reef are 
the most favourable for coral growth. Hence, if a bank of 
coral be established below water, there is a tendency in the 
coral at its margin to grow both outwards and upwards, so 
that at last an atoll form is developed. As the rim 
approaches the surface, it is raised by the piling up of 
debris, broken off by the waves, and may, in some cases, 
also be upheaved. But the waves, tides, currents, &c., 
tend also to destroy parts of the island, so that there is a 
constant struggle going on between the constructive and 
destructive agencies. The author then proceeds to apply 
his theories to the formation of the Maladive atolls, remark- 
ing in conclusion : — ‘ However one looks at the subject one 
must realise that the laws governing the formation of coral 
reefs are exceedingly complex, and that many circum- 
stances have to be taken into account before any perfect 
explanation of their structure can be obtained.’ 
While these sheets were passing through the press a 
letter written by Mr. H. B. Guppy to Mr. J. Murray ap- 
peared in Nature (vol. xxxix. p. 236), giving some account 
