"Between the islands of Bahuluvvang and Tambolungan our bank extends in a direction 

 from North to South covered by a layer of water averaging from 6 to 9 metres deep ; but 

 towards the West and East of the bank the layer of water deepens fairly rapidly, attaining a 

 depth of 10, 14 to 18 metres, becoming at last very deep. On this bank Lithothamnia live in 

 great abundance; living corals are entirely wanting. The net, in fact, only brought up scanty 

 and dead fragments, which the current had clearly carried there after detaching them from 

 neighbouring coastal reefs. The force of the current is great. During the ebb it sets west, while 

 the dood tide sets east. If the bank is bare of corals - - which is seldom the case in the 

 Archipelago - - this is due to the current which, carrying along sand and débris of Halimeda, 

 covers up the corals that are trying to establish themselves there and smothers them out of 

 existence. This is not the fate of the Lithothamnia. As we have said, the current rolls them 

 sometimes in one way sometimes in another accordino- as it is running- East or West, fiood or 

 ebb. In places where the play of forces is suitably balanced between the strength of the current, 

 the vveight of the nodules of Lithothamnia and the weight and mass of the detritus, the nodules 

 remain free and uncovered and are able to form a bank. But in places where local accumulations 

 of detritus are formed, in the same direction as the current, those bands of which we have 

 spoken appear; these are less favourable to the development of Lithothamnia and become less 

 and less so in proportion as they grow more accentuated". 



In Arctic seas Foslie ') tells us, that Lithothamnion-banks often consist of only one 

 species. Near Nowaja-Zemlya and Spitsbergen Lithothamnion glaciale will cover the bottom 

 for several miles and on the coast of Iceland and northern coast of Norvvay Lithothamnion 

 i ngeri will occur in masses. So also Lithothamnion investiens, a species nearly related to the 

 former, covers in certain places on the north-coast of Norway the bottom for several miles. 

 In the Malay Archipelago it appeared to us, that one or other species usually was predominant 

 but other species would not be entirely lacking, and incrusting forms can almost always be 

 found, when attentivelv searched for. For the Lithothamnia, besides contributine greatlv to the 

 bulk of a reef or bank by their branching species, will also play an active part in the building 

 up of a reef by their incrusting species, which grow over shells, corals or other Lithothamnia, 

 cementing all these together into one solid mass. The value of this cementing cannot be over- 

 estimated on a reef, where the waves of the sea are continually washing off the looselying masses. 

 A most dangerous enemy to Lithothamnia is another family of algae : the boring algae. 

 These algae were first made known by Bornet and Flahault -). They belong as a rule to 

 filamentous blue, green or even red algae. The study of these plants has as vet only been 

 begun and their universal distribution and their power of disintegrating even rocks, will become 

 more and more recognized. 



■ Here and there in literature I have met with the expression "green Lithothamnia" . I do 

 nut believe that there exists one single green species of Lithothamnion. If knolls or crusts of 

 these plants are green, this is due to boring algae, which are found according to my experience 



1) M. Foslie. The- Lithothamnia of the Laccadive and Maldive Islands. Fauna and Geogr. of the Mald. and Lace. Archipelagoes. 

 vol. II, part. 4. 



2) Bornet et Flahault. Sur quelques plantes vivant dans Ie test calcaire de» Mollusqües. Buil. Soc. bot. de France. t. XXXVI. 



