248
C. M. YONQE
such as Colpophyllia natans (with which Gonimtrea mpera could be
compared) there is little difference from one area to another (Goreau,
1959a, 1961a). Nevertheless, the environment may exert a considerable
constraining influence, for instance in the formation of flattened
colonies of Sidermtrea radians on intertidal beach rock compared with
rounded colonies in still, deeper water (Yonge, 1935b). '
These laboratory findings were confirmed by Goreau in the field.
Further evidence was also obtained of discontinuous and irregular
growth within a single symmetrical colony and also between individual
colonies of the same species, conclusions already reached by earlier
workers. The probability that calcification is not a continuous process is
indicated by the lamellated nature of the skeleton. Field experiments
on a wide range of corals revealed that there was no necessary correlation between rate of calcification and relative abundance of different
species on the reefs. It appears that the race is not necessarily to the
most quickly growing species.
Particular interest attaches to studies on Manicinn arwEata
(Goreau and Goreau, 1960b). After a period of initial attachment, this
interesting coral lives free on the surface of sand and so occupies the
same habitat as the Indo-Pacific fungids (Yonge, 1935a). Here also the
growth rate falls with increasing size (i.e. age). As shown in Fig. 13,
the specific calcification rate in the smallest colonies was seventy-six
times greater than in the largest. Senescence (perhaps by reduction in
cell division) could account for this, as postulated by Motoda for
Gonimtrea. Goreau and Goreau do not think that zooxanthellae are
in any way concerned. Unlike related massive corals, the ratio of surface area to volume (measured respectively by total nitrogen and
weight) remains almost constant in this species. This is due to the
increased folding of the surface with age which is rightly regarded aa
an adaptation for life in sand. As described and illustrated by Yonge
(1935a), M . ( = Maeanclra) areolata can clear itself when covered with
sand by a distension of the coenosarc with water. It can also, as
observed by Goreau and Goreau, by similar means right itself after
being turned over. These activities demand an extensive coenosarc
capable of being raised well above the surface of the skeleton. The
fungids are capable of similar movements.
XI. EFFECT OF LIGHT
The supreme influence of light on the growth of hermatypic cords
has long been apparent. As stated by Umbgrove (1947), " the depth
of the living reef is correlated with light penetration ". Earlier evidence
C. M. YONQE
such as Colpophyllia natans (with which Gonimtrea mpera could be
compared) there is little difference from one area to another (Goreau,
1959a, 1961a). Nevertheless, the environment may exert a considerable
constraining influence, for instance in the formation of flattened
colonies of Sidermtrea radians on intertidal beach rock compared with
rounded colonies in still, deeper water (Yonge, 1935b). '
These laboratory findings were confirmed by Goreau in the field.
Further evidence was also obtained of discontinuous and irregular
growth within a single symmetrical colony and also between individual
colonies of the same species, conclusions already reached by earlier
workers. The probability that calcification is not a continuous process is
indicated by the lamellated nature of the skeleton. Field experiments
on a wide range of corals revealed that there was no necessary correlation between rate of calcification and relative abundance of different
species on the reefs. It appears that the race is not necessarily to the
most quickly growing species.
Particular interest attaches to studies on Manicinn arwEata
(Goreau and Goreau, 1960b). After a period of initial attachment, this
interesting coral lives free on the surface of sand and so occupies the
same habitat as the Indo-Pacific fungids (Yonge, 1935a). Here also the
growth rate falls with increasing size (i.e. age). As shown in Fig. 13,
the specific calcification rate in the smallest colonies was seventy-six
times greater than in the largest. Senescence (perhaps by reduction in
cell division) could account for this, as postulated by Motoda for
Gonimtrea. Goreau and Goreau do not think that zooxanthellae are
in any way concerned. Unlike related massive corals, the ratio of surface area to volume (measured respectively by total nitrogen and
weight) remains almost constant in this species. This is due to the
increased folding of the surface with age which is rightly regarded aa
an adaptation for life in sand. As described and illustrated by Yonge
(1935a), M . ( = Maeanclra) areolata can clear itself when covered with
sand by a distension of the coenosarc with water. It can also, as
observed by Goreau and Goreau, by similar means right itself after
being turned over. These activities demand an extensive coenosarc
capable of being raised well above the surface of the skeleton. The
fungids are capable of similar movements.
XI. EFFECT OF LIGHT
The supreme influence of light on the growth of hermatypic cords
has long been apparent. As stated by Umbgrove (1947), " the depth
of the living reef is correlated with light penetration ". Earlier evidence