330 J. STANLEY GARDINER. 



some period certainly less than 3 years, and probably not moi-e than 2 years and 10 months, to 

 have grown up from ova to their present size. 



The physical conditions in the Hulule canal cannot be said to be especially inimical or 

 favourable to coral growth. Strong currents pass in and out of the atoll between Hulule 

 and Male, so that there is ample change in the neighbouring waters. The coral growth is 

 luxuriant on the reefs to the west of Hulule, and the different corals grow fairly evenly in 

 height, no genera being particularly vigorous. During the north-east monsoon there is a 

 considerable sweeping out of mud, weed and sand from the shores of the island, which must 

 be injurious to coral life. One may deduce from the appearance of the western passages 

 into Minikoi atoll in the south-west monsoon, and fi-om that of many of the artificial canals 

 in the Maldives opening to the east in the north-east monsoon, that in the south-west 

 monsoon the bottom of our canal would be swept bare of all sediment, absolutely down to 

 the rock. The same canal, too, feeds no wide stretch of water so that the currents in it would 

 not be of any gi'eat force. The canal, accordingly, in the south-west monsoon should be especially 

 favourably situated for the gi'owth of corals. Coral larvae could scarcely succeed in establishing 

 themselves in the north-east monsoon on account of the mud, whereas the opposite monsoon 

 should be most auspicious for their fixation. Indeed, it is probable that all the specimens 

 would have commenced to grow in the latter monsoon, and that they would hence represent 

 three growth periods of less than 3, 2 and 1 years. 



The accompanying Table of the specimens serves to explain itself (p. 331). I have not yet 

 worked out my coral collections, so that the naming of the species must be taken as only ajjproxi- 

 mately correct. The important point is to know the form of growth in the genus — it is very 

 unlikely that the rate of growth in a genus differs materially in closely-related species — and the 

 specific name, or some other indication, is given in each case to show the facies. I have added 

 to the form of my table, as originally published, the approximate horizontal area each coral 

 covers in its position of growth, as far as the latter can be perceived, and also the height of 

 each above its true horizontal base. As the colonies had been drying for two years, I have 

 only given one weighing in this state. They were then soaked in water and weighed in the 

 same until the resulting weight became constant; the volume alone, however, of the broken 

 fi-agments was measured. 



It is important to observe a second time that the above specimens must all have grown up 

 to their present size witltin a period of 3 years ab ovo. Further, they were all obtained out of an 

 area of 4 square yards, or 33416 sq. cms. Their position in the canal, some distance from its 

 outer end but more or less in the centre, would certainly not theoretically have been the most 

 luxuriant for coral growth, and indeed was selected rather as representative of the whole channel. 

 Most of the corals were attached, and must have grown in the position in which they were 

 obtained. The Fungia and two other free forms, Orbicella (No. 8) and Monttpora saxea (No. 20), 

 if they did not actually gi-ow within the area, can only have originated in its immediate vicinity; 

 in no case is it possible to suppose that they can have come fi-om the reefs at the sides of 

 the canal. 



The rate of growth of the reef as a whole can be calculated for say 1000 years by several 

 methods: — (1) The specific gravity of fine sand-rock being 2-48 (average of 10 samples), the 

 corals may be estimated in this condition, and will give a deposit over the area of 85 cms. 

 (2) With the specific gravity 178 (see Table), the deposit would be 123 cms. (3) Taking merely 

 the area 3986 sq. cms., known to be actually covered by the corals themselves, the growth. 



