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SECTION YI. 

 BIOLOGY OF THE REEF-FORMING ORGANISMS AT FUNAFUTL ATOLL. 



By ALFilED E. FiNCKH. 



(1) General Description of a Biological Section Across the Atoll approximately from 



West to East. 



A general description of a Biological Section across the atoll will perhaps best 

 convey to the mind the distribution of the various reef-forming organisms, as regards 

 their relation to the ocean and lagoon respectively. 



Beginning at the western ocean face of the atoll, near the southern end of the islet 

 of Fualopa, our section traverses the lagoon and strikes the main island, Funafuti, on 

 the lagoon platform which extends out from the north end of the sandy beach near 

 the village. Thence it passes across the platform and over the main island and 

 ultimately runs out over the ocean platform in the neighbourhood of the " line of 

 plugs" the "permanent reference marks" of Mr. Halligan's report, situated east 

 of the main diamond-drill bore. The western rim of the atoll, our starting point, is of 

 extremely irregular width. The irregularity of outline is, however, mainly on the 

 lagoon side, the boundary of the atoll oceanwards coinciding with the general contour 

 of the atoll. The reef platform in its entire width is approximately of the 

 same level. 



The superficial part of the ocean platform will be described first, the deeper parts 

 later. On the ocean side, up to as far in as the wash of the waves reaches at low- 

 water spring tide, the reef platform is densely covered with vigorously growing 

 organisms. Of these the thinly branching Lithothamnion is the most abundant. 

 This alga appears in small isolated shrub-like clusters from 1 inch to 5 inches in 

 diameter, and varying similarly in height. Between these clusters many small 

 coralla of the species Madrepo7^a loripes. Brook, are seen, while they themselves grow 

 in such numbers and so close to one another that it is impossible, while walking on 

 this part of the reef, to put one's foot down without treading on them. The founda- 

 tion on which these grow is the solid rock of the reef platform which extends to the 

 very edge of the platform. Near the edge are other coral forms, also the Lithothamnio7i 

 of the lichenous and knobby forms, but no Porites nor lleliopora ccerulea. These all 

 help to form a complex covering of living material for the rocky platform. No one of 

 these species, however, forms patches of any considerable size, each being prevented 



