Protandry and Senescence of Corals. 469 



adjacent sides. The Minikoi specimens correspond to the last 

 state found in Flabellum, and it is interesting to remark that the 

 two colonies examined were the only living ones found in this 

 locality, although dead corolla were very constantly turned up. 



One part of the reef at Rotuna, some hundreds of square 

 yards in extent, was nearly completely overgrown by a coral, 

 which I identified as Madrepora pulcra Brook, var. alveolata 

 Brook 1 . This is one of the staghorn-growing species of the genus 

 with widely separated branches, and was not found save in this 

 single area. Most of the stems were dead at the base, the coralla 

 in some parts of the area having no living polyps at all. In three 

 living twigs, which I examined, all the polyps of every part were 

 female. The ova were very far from regular, some of the polyps 

 having on their mesenteries isolated ova, others no ova at all, 

 though they had evidently recently possessed them. All the 

 branches over the whole area were evidently dying. My exami- 

 nation, which was made in 1898, was undertaken to ascertain the 

 cause, but was without result. No trace of silting up by mud 

 was found, nor was there marked shrinkage and decay such as 

 results from drying up owing to undue exposure to the sun and 

 air. The endoderm was everywhere devoid of food granules, but 

 except in its staining properties appeared healthy. The con- 

 dition again is only paralleled by that of the largest Flabellum, 

 suggesting that the same operative cause may have acted in 

 both cases. 



Death of the corals on reefs is common, and has been observed 

 by most workers thereon. In some cases it may have been due 

 to exposure, in others to silting up or even too high a tempera- 

 ture, but in such not one nor two species of corals nor even 

 genera would be affected,' but all coral growth on the area. In 

 addition there is much death, which cannot properly be assigned 

 to environmental causes, where single colonies die or a number 

 of colonies of a single species in a particular area. Separate 

 dead colonies, enormous masses perhaps, are often found where 

 neighbouring colonies of the same species, both large and small, 

 are nourishing. 



A different case — here and there observed in the Maldives — 

 would be that where a species or genus of corals was absent in 

 the living condition from one reef, while on the next with 

 apparently absolutely similar conditions it was perchance growing 

 luxuriantly. Living Coeloria daedalea was absent from the west 

 or seaward reef of Addu Atoll off Maradu, while Leptoria tenuis 

 was extremely common, forming large colonies. The reverse in 

 these two species was the case on the seaward reef off Midu to 

 the north-east of the same atoll. Elsewhere in the Maldive 

 1 Pruc. Zool. Soc, 1898, p. 259. 



33—2 



