122 THE GREAT BARRIER REEF. 



shape and size, but of more variable colours, that were dredged up in a tangled mass in Cleveland 

 Ba\', off Townsville. 



The high-water bands of flotsam and jetsam on the Cairn Cross beach contained, as do many 

 of those coral-islets in the Barrier district, thousands of the chambered spiral shells of the 

 Belemnitoid genus Spirula. The habitat and natural conditions under which this interesting little 

 cephalopod flourishes are among the unsolved mysteries of science. It was expected that 

 the Challenger expedition would throw a flood of light on the life phenomena of the type. A 

 single perfect specimen dredged off Banda, in 360 fathoms, and some dead shells collected, as 

 at Cairn Cross, on the beach of Raine Island, recently described, and a single dead shell from 

 a depth of 2,000 fathoms off the north coast of New Guinea, are the sum total of the material 

 illustrative of the genus Spirula obtained throughout the cruise, as recorded in the excellent 

 report on the Cephalopoda of the expedition, drawn up by Mr. W. E. Hoyle, Naturalist 

 on the editorial staff of the Challenger reports. It is remarked by Mr. Hoyle that the single 

 shell, dredged from 2,000 fathoms north of New Guinea, had a dead shell of a barnacle attached 

 to it, and that this Spirula had almost certainly fallen from the surface of the sea to the depth 

 at which it was taken. 



A similar association of an originallv floating fulcrum with an attached organism, distin- 

 guished a specimen found by the author on the Cairn Cross beach. This was represented 

 b}' a rounded lump of pumice-stone, about 3A inches in diameter, to which two young coralla 

 of the Madrepore, Pocillopora danitconiis, were attached. The bases of the coralla are each about 

 I5 inch wide, and the rudimentary tuberculate branchlets are about ^ of an inch high. This speci- 

 men was thrown on the beach in a buoyant condition, as is evident by its still floating lightl}' even 

 in fresh water. The attached Pocilloporae probably represent the growth of a few months onl}', 

 and would, at an early date, have completely invested the pumice-stone fulcrum, and caused it to 

 sink. Dredged up from deep water in a perfect, if dead, condition, this typical reef-coral, with the 

 concealed pumice nucleus, would have proved a very apple of discord among biologists. In the 

 condition in which it was found, the specimen throws a new light on the means of reef-coral 

 distribution. The two attached coralla indicate the probability of coral-germs floating abundantly 

 at the surface of the sea, and that by attaching themselves freely to such objects as floating pumice 

 they may be distributed through the most widely-extended areas. The sudden and otherwise inex- 

 plicable disappearance of tracts of floating pumice from districts where they have previous!}' 

 abounded, may be also easily accounted for by the attachment of coral or other organic germs. 

 Evidence was elicited by the author, in connection with the specimen now under discussion, from 

 a resident in Borneo, that the pumice-stone ejected during the eruption of Krakatoa, and distri- 

 buted for thousands of square miles, disappeared within a short time over extensive areas through 

 the abundant attachment ol a species of barnacle to the floating masses. 



One of the strongest attractions to ordinary passengers favoured with an opportunity of 



