336 J. STANLEY GARDINER. 



abundant in the velu of Hulule, while in Minikoi it was only once secured. Generally it was 

 local in the Maldives, but, where present at all, it usually was found in considerable numbers. 

 It never occurs in coral in an advanced state of decay nor in rock masses. 



A second Mollusc, a small sjDiral Gastropod, is also in places abundant in corals, but 

 whether it makes its own holes or not is uncertain. It may be as is Vermetus enclosed by 

 the growth of the coral. In any case it is only local, mainly affecting Leptoria and other reef- 

 loving Astraeidae. 



Sipunculoidea are prominent forms in breaking up almost any large block of coral from 

 any position on the reefs or from any depth found on them, but only the bases of branching 

 colonies are affected. These borers are perhaps more numerous in lagoon masses than in blocks 

 from seaward reefs. This may be due to the former generally being larger, and it may be that 

 equally large colonies from say 10 fathoms outside and inside an atoll would be similarly 

 affected. While not quite absent from dead coral-rock — of the reef flat or an uj^heaved pinnacle, 

 etc. — the boring Sipunculids undoubtedly prefer a coral which is to some degree living. Their 

 holes are perfectly round and smooth, and ramify in every direction through the coralla. In 

 size they seldom exceed the half or third of the diameter the animal assumes when freed. 

 How the holes are made is not in most genera quite clear. When in the living state, the 

 bodies of none have any acid secretion, so that their holes are presumably made by friction. 

 The body is slightly swollen out, and, the skin being rough, forms a firm support from which 

 the animal can act. The genera represented were PJiyscosovia, Phascolosoma, Aspidosiphon, 

 Gloeosiphon, and Lithacrosiphon, and an account of the species obtained with further notes will 

 be found in Mr Shipley's Report on the Group (pp. 131 — 140). 



Polychaeta are perhaps really the most important boring animals in coral rock, although 

 the actual forms are inconspicuous and of small diameter^ In coral reefs at least some specimens 

 can be obtained from every rock below and between tide marks. All large coral masses are 

 bored into and penetrated by their tubes, which bend and twist in every direction. The surface 

 at the edge of the reef is made rotten for some inches by their borings, and the section of the 

 broken base of a coral often appears as a regular sieve from their holes. The finer-textured 

 corals are principally affected, but all corals and rocks are attacked, so long as they have a 

 fixed base of support. Fomis with calcareous or other tubes that grow with the corals are also 

 bad, as they make them peculiarly brittle, and their holes form a lodgment for other organisms, 

 whose subsequent destructive work is greater. From their prevalence in every rock be it of 

 coral, sand or nullipore, the total effect of the Polychaeta must be enormous, and they must 

 certainly be regarded as the prime and most effective agents in the breaking down of coral rocks. 



Of the families of Polychaeta, found as borers in the corals and rocks of the Maldives, by 

 far the most numerous and important are the Eunicidae, which in large numbers burrow 

 into every rock and coral, extending in the latter up to and often penetrating the polyp tissues. 

 They are the chief cause of the rotting of the rock of the reef flat, and are abundant in the 

 lagoons as well, coral masses obtained from upwards of 40 fixthoms being riddled by their holes. 

 The Lumbriconereidae are less numerous, principally affecting recently formed coral, especially 

 of the seaward reefs and passages. The Scoleciformia may bore into any rock, but are not 

 common except in such as are already in a state of decay. The same remark applies also to 

 the Phyllodocidae, but this family was f;ir scarcer in the Maldives than at Funafuti. The 

 Nereidae and Amphionomidae are not properly borers, but isolated forms may sometimes be 

 found in tubes in the rock, which, if they have not made, they have certainly enlarged. 



