192 THE GREAT BARRIER REEF. 



captivity, that few biologists have had an opportunity of observing it. Some phenomena of 

 interest were associated with the author's earlier endeavours to make himself acquainted with 

 the aspect and the structure of its living elements. The species was first obtained by him in 

 the year 1889, in the neighbourhood of Warrior Island, Torres Strait; but, although placed in 

 constantly renewed sea-water, and carefully observed night and day, the polyps refused to expand. 

 In June of the subsequent year, 1890, the same species was obtained from the Mid-Brother reef 

 in the neighbourhood of Adolphus Island, at the entrance to the same Strait, special facilities for 

 visiting the district having been then accorded the author by Captain Dawson and the officers of 

 H.M.S. Rambler, at that time engaged in making a new survey of the scene of the disastrous 

 Quetta wreck. 



Specimens of Heliopora obtained on this occasion were kept alive for some days on board the 

 Rambler, and were ultimately brought on to Thursday Island in the living state, and deposited 

 in one of the coral-pools at Vivien Point, utilised by the author for the cultivation of mother-of- 

 pearl shell. During its retention on board-ship, the phenomena here recorded were observed, and 

 accepted as furnishing a new clue to the affinities of this coral. The author not being cognizant 

 at the time of the results of Prof. Moseley's investigations, and having Mr. Dana's work indicat- 

 ing its Hydroid relationship alone to refer to, the organism was approached with the anticipa- 

 tion of encountering a much modified Hydroid polyp, nearly akin, perhaps, to Millepora. How 

 far the anticipation was realised will be shown. The surface of the corallum of Heliopora, it 

 should be explained in the first place, is perforated with cylindrical pores of two dimensions, larger 

 and fewer ones, which have a diameter of less than a millimetre, and, interspersed among 

 these, innumerable smaller pores about one-fourth of the diameter of the larger ones. Within 

 a few hours after bringing specimens from the reef and placing suitable fragments in sea- 

 water, the presence of living organisms was made apparent, in the form of two slender trans- 

 parent tentacles, which were seen protruding from each of the smaller pores, followed by a short 

 portion of a cylindrical semi-transparent body. The aid of a pocket-lens was necessary to make 

 out these details distinctly. At first sight, it was suspected that the organisms observed were 

 allied to the bitentaculate Hydroid zoophyte, described many years since by Mr. P. H. Gosse 

 under the title of Lar sabellarum ; which inference, had it proved correct, would have given 

 substantial support to the theory of the relationship between Heliopora and Millepora, and other 

 coral-building Hydroids. 



On the author's following up the superficial examination of the corallum, by making sections 

 through its substance, and thus laying open the pores from which the tentacles protruded, a totally' 

 unexpected result was arrived at. It was then shown that the protruding tentacles were the 

 terminal appendages of a long slender, setiferous, worm, subsequently ascertained to belong- 

 to the same family as, and to be very closely allied to, Leucodore ciliata, a species that has of 

 late years been accredited with compassing the destruction of the New South Wales oyster- 



