218
C. M. YONOE
two halves then exposed to different environments. A long-term programme of such experiments would be of great taxonomic value. Further
possibilities are presented by the fusion of recently settled planulae
which then give rise to colonies having the same form aa those which
arise from a single planula. Fusion of planulae has been observed in
species of Siderastrea, Pocillopora and Porites and also in Manioina
areolata. Identically shaped oval colonies of the last of them may
consist of one, two or three ‘‘ valley ” systems indicating formation
from one to three original planulae (Yonge, 1935a). There irs here, it
seems, a means of determining the effects of genetic constitution and
of the environment. If planulae of known origin could be induced to
settle together (and although in many planulation does occur at different
phases of the moon there appears to be considerable overlap (me
Atoda, 1947a, b, 1951 b, c)) successful fusion would indicate origin from
different growth forms of the same species, failure to fuse origin from
different species. It is, of course, possible that composite colonies might
be produced, particularly if allied species with different breeding seasons
could be induced to breed at the same time. This would be of no leas
interest, especially if the growth of the composite colony could be
compared with that of each parental species.
Factors influencing the settlement of planulae have never been
adequately analysed. Working on species of Pocillupora, BeriatopOra,
Acrhelia and Euphyllia, Kawaguti (1941b) found that within a certain
range of light intensity, progressively lower in the order listed, all were
positively phototactic, the reaction reversing in higher light intensities.
All were negatively geotactic. Distribution of the adult colonies bore
some relation to the reactions of their plariulae. These in turn appeared
to be correlated with the concentration of zooxanthellm. Edmondson
(1946) tested the reaction of plmulae of Pocillupora &micorn&,
C y p h t r e a ocellini and the ahermatypic Dendrophyllda man&. Hie
results indicate the greater abundance in surface waters of planulae
during darkness or subdued light, i.e. a major effect of negative geotaxk.
Like Kawaguti, he noted positive thigmotaxis. He observed reactions
to temperature and salinity changes but more significantly noted that
while the larvae of Cyphastrea and Dendrophyllia would both settle in
total darkness, the yoimg polyps of the latter (without zooxanthellae)
survived for up to seven months, whereas those of the former soon died.
Planulae of these two species, but not of P . damicornis, tended to settle
in aggregations.
I n a series of papers (1947a, b, 1951a, b, c, 1953), Atoda has described
planulation, planulae, settlement and early development in P m i w a
damicornis cespitosa, Stylophora pistillata, Acropma brtiggemanni,
C. M. YONOE
two halves then exposed to different environments. A long-term programme of such experiments would be of great taxonomic value. Further
possibilities are presented by the fusion of recently settled planulae
which then give rise to colonies having the same form aa those which
arise from a single planula. Fusion of planulae has been observed in
species of Siderastrea, Pocillopora and Porites and also in Manioina
areolata. Identically shaped oval colonies of the last of them may
consist of one, two or three ‘‘ valley ” systems indicating formation
from one to three original planulae (Yonge, 1935a). There irs here, it
seems, a means of determining the effects of genetic constitution and
of the environment. If planulae of known origin could be induced to
settle together (and although in many planulation does occur at different
phases of the moon there appears to be considerable overlap (me
Atoda, 1947a, b, 1951 b, c)) successful fusion would indicate origin from
different growth forms of the same species, failure to fuse origin from
different species. It is, of course, possible that composite colonies might
be produced, particularly if allied species with different breeding seasons
could be induced to breed at the same time. This would be of no leas
interest, especially if the growth of the composite colony could be
compared with that of each parental species.
Factors influencing the settlement of planulae have never been
adequately analysed. Working on species of Pocillupora, BeriatopOra,
Acrhelia and Euphyllia, Kawaguti (1941b) found that within a certain
range of light intensity, progressively lower in the order listed, all were
positively phototactic, the reaction reversing in higher light intensities.
All were negatively geotactic. Distribution of the adult colonies bore
some relation to the reactions of their plariulae. These in turn appeared
to be correlated with the concentration of zooxanthellm. Edmondson
(1946) tested the reaction of plmulae of Pocillupora &micorn&,
C y p h t r e a ocellini and the ahermatypic Dendrophyllda man&. Hie
results indicate the greater abundance in surface waters of planulae
during darkness or subdued light, i.e. a major effect of negative geotaxk.
Like Kawaguti, he noted positive thigmotaxis. He observed reactions
to temperature and salinity changes but more significantly noted that
while the larvae of Cyphastrea and Dendrophyllia would both settle in
total darkness, the yoimg polyps of the latter (without zooxanthellae)
survived for up to seven months, whereas those of the former soon died.
Planulae of these two species, but not of P . damicornis, tended to settle
in aggregations.
I n a series of papers (1947a, b, 1951a, b, c, 1953), Atoda has described
planulation, planulae, settlement and early development in P m i w a
damicornis cespitosa, Stylophora pistillata, Acropma brtiggemanni,