THE BIOLOGY OF COB& REEF8
217
interesting results. Thus Wells (1954) reduoed five species of POT&%
to one, P. lichen. On the other hand, Boschma (1948b, 1949, 1950)
reversed Hickson’s ruling by re-establishing, on the basis of the form of
the skeleton and of the ampullae, eight formerly deacribed species of
Hillepora and adding a new species, making ten in all. Crossland (1962)
added yet another species.
Boschmi~’8 explanation (1948a) of the diversity of forms in Milkpora
-it may well serve for many other genera of hermatypic coralsinvolving both species and growth forms deserves to be quoted. ‘‘ There
are a number of species of Hilkpora, each of which is so strongly
variable that under the influence of external conditions it may w u m e a
form which is more or less typical for another speciee. If a Nillepora
larva happens to become fixed on a spot where the conditions of existence are ideal for the species, it grows out to a colony of the typical
form. If it happens to become fixed on a spot where the conditions of
existence for this particular species are unfavourable it may grow out to
a colony with a growth form quite different from that of the typical
form. If it happens to become fixed on a spot where the conditions of
existence are altogether unsuitable for this particular species (although
other species of Millepora may find here ideal conditions for a luxuriant
development) the young colony dies. It is not to be denied that certain
species which have a pronounced preference for distinct parts of the
reefs in these parts only develop into colonies of the typical shape. A
good example forms M . platyphyUa that attains ite most vigorous
growth (the “ honeycomb facies ”) on the surf-swept edge of the reefs
only, and changes into a leafy form when living in the quieter water of
the lagoon.”
As formerly stressed (Yonge, 1940), the great mccms of the
Scleractinia may well be due to the presence of speciee highly adapted
for a particular habitat dong with others capable of modification to
produce a variety of growth forms capable of life in a variety of
environments. The relation between form and the two factors of light
and water movement is shown in the work by Abel(l969) on the ahermatypic Mediterranean coral, Claducera cespito8a. SimiIar observations
could very suitably be made on tropical reef-builders.
IV. SETTLEMENT OF F’LANULAE
Final distinction between growth forms and species can only be
achieved by observations in the field such as were carried out in the
course of the Great Barrier Reef Expedition when marked cords were
moved from one environment to another or colonies were split and the
217
interesting results. Thus Wells (1954) reduoed five species of POT&%
to one, P. lichen. On the other hand, Boschma (1948b, 1949, 1950)
reversed Hickson’s ruling by re-establishing, on the basis of the form of
the skeleton and of the ampullae, eight formerly deacribed species of
Hillepora and adding a new species, making ten in all. Crossland (1962)
added yet another species.
Boschmi~’8 explanation (1948a) of the diversity of forms in Milkpora
-it may well serve for many other genera of hermatypic coralsinvolving both species and growth forms deserves to be quoted. ‘‘ There
are a number of species of Hilkpora, each of which is so strongly
variable that under the influence of external conditions it may w u m e a
form which is more or less typical for another speciee. If a Nillepora
larva happens to become fixed on a spot where the conditions of existence are ideal for the species, it grows out to a colony of the typical
form. If it happens to become fixed on a spot where the conditions of
existence for this particular species are unfavourable it may grow out to
a colony with a growth form quite different from that of the typical
form. If it happens to become fixed on a spot where the conditions of
existence are altogether unsuitable for this particular species (although
other species of Millepora may find here ideal conditions for a luxuriant
development) the young colony dies. It is not to be denied that certain
species which have a pronounced preference for distinct parts of the
reefs in these parts only develop into colonies of the typical shape. A
good example forms M . platyphyUa that attains ite most vigorous
growth (the “ honeycomb facies ”) on the surf-swept edge of the reefs
only, and changes into a leafy form when living in the quieter water of
the lagoon.”
As formerly stressed (Yonge, 1940), the great mccms of the
Scleractinia may well be due to the presence of speciee highly adapted
for a particular habitat dong with others capable of modification to
produce a variety of growth forms capable of life in a variety of
environments. The relation between form and the two factors of light
and water movement is shown in the work by Abel(l969) on the ahermatypic Mediterranean coral, Claducera cespito8a. SimiIar observations
could very suitably be made on tropical reef-builders.
IV. SETTLEMENT OF F’LANULAE
Final distinction between growth forms and species can only be
achieved by observations in the field such as were carried out in the
course of the Great Barrier Reef Expedition when marked cords were
moved from one environment to another or colonies were split and the