168 J. STANLEY GARDINER. 
of Goifurfehendu, Gafaro and Wattaru. In Fadifolu also there is a very marked destruction 
of the central reefs, and one even was found to have been resolved into a series of 
patches. 
The reefs against the passages into any bank are subject to strong tidal and other 
currents. both in and out, which for all practical purposes reach the bottom, the friction being 
negligible. They hence experience a rapid change of water, which must be advantageous to 
their organisms, but against this the force of such strong currents and the mud they carry 
out of the bank must be injurious. Their slope is commonly gradual to about 6 fathoms 
and then precipitous to within 5 fathoms of the bottom. Where the reef projects as two 
points on each side of a passage, there is no doubt of what is happening. The edge 
of each reef is covered with nullipores, which for ever hold each inch they save from 
the sea. Only a few corals are found, but the slope in such a position in North Mahlos 
is less precipitous and nearly completely covered with nullipores, as deep as the eye can 
see. There is no doubt in many places but that the encircling reef is closing itself up. 
That this everywhere is the case in the Maldives, I cannot say, but it seemed to be the 
rule in every atoll we visited; in many passages we found no change, and in a few a 
possible compensation in an enhanced depth. Where there is a long passage between two 
reefs, as between Fainu and Kenurus, the nullipores are only found on the reefs at their 
seaward ends, and off the latter island there is a distinct shallow horn growing northwards 
closing the passage. The same is the case north of Inguradu, and Mr Forster Cooper 
noted it also in several of the other reefs of the east rim. On the west rim I found 
the channel much restricted between Ma-faro and Kuda-faro, and observed along the whole 
side the broader western ends of all the faro. Generally speaking, the reefs on either side 
of passages belong everywhere to the category of outgrowing ones, but it is only the very 
outer ends of these that can ever meet by the spreading of the reefs themselves. Here 
again, as the strength of the currents must increase, growth will be less rapid as the rim 
becomes more perfect. In Mahlos and Miladumadulu the outgrowth of points is quite clear, 
but in more perfect atolls no definite change could be proved. Even where found, it was 
never certain that it was a function of the last 60 years, as the tendency of the cartographers 
would have been to round off every point and reef. 
There is also in some of the passages an upgrowth from the bottom, which assists 
materially in closing them up. In the chart of North Mahlos no less than 10 shoals or 
reef-patches, that have not quite reached the surface, are marked in the passages. These 
patches differ from those in the “jungle” in that they are the centres of vigorous organic 
growth. They are not gaunt rocks but hills, with steep though not precipitous sides, except 
perhaps towards the lagoon, and are covered all over with corals, nullipores, and other 
organisms. Of corals Dendrophyllia! abounds in all the passages, and dead corals are at 
once covered over with Polytrema and Nullipores (Lithothamnion). The passages are swept 
clean of all sand, but some coral must remain. In some of the passages of other banks 
we found fresh shoals that can hardly have 
1 Dr MacMunn in a Report ‘‘On the Pigments of Coeno- 
psammia, Dendrophyllia and Heliopora, etc.” in the same 
Part of this Publication points out the presence of chlorophyll 
among the other pigments and discusses its meaning. Should 
the chlorophyll assist in the nutrition of the polyps of 
Dendrophyllia, its habitat in the passages should be an 
existed before, but we did not examine the 
exceptionally favourable one owing to the constant change 
of water. The presence of a chlorophylloid pigment in the 
skeleton of Heliopora—hence completely outside the polyps— 
is of the greatest interest, and so far as I am aware without 
parallel in the animal kingdom. 
