378 Dr. E. P. Wrio-ht oti the Animal 



t)' 



I could see, wlien the sea was tranquil, the surface of the reef 

 as distinctly as if it were only covered by an inch or two of 

 water. I had walked over this and other coral-reefs so very 

 often, that I had not on this occasion much hope of discover- 

 ing anything new. The surface on which I walked was a 

 perfect carpet of a pretty bluish-green Xenta, interspersed 

 here and there with patches of a bright scarlet and of a green 

 alga. Sometimes, when a small heap of dead coral was met 

 with and turned over, a large cuttlefish would endeavour, and 

 sometimes successfully, to get over the edge of the reef, and 

 then away. Large specimens of that fine Holothuroid MUl- 

 leria nobi'h's, and at intervals a Ciilcita, would be seen and col- 

 lected. The edges of the gullies actually bristled with the 

 long spines of Diadema Savignyi. The pain caused by in- 

 cautiously touching the spines of the species of this genus is 

 very great — so great that I have had my arm and hand quite 

 benumbed by it for some hours. At one spot, near the very 

 edge of deep water, my foot sank in some soft yet brittle stuff, 

 and, from the sensation, I knew I had crushed some coral- 

 structure that I had not before met with. On examination, 

 this proved to be a bunch of the Tuhipora^ which was grow- 

 ing parasitically on a large rock of Madrepore ; and now that 

 I found the habitat of this species, I had no difficulty in find- 

 ing any quantity of it. Some masses were two feet in dia- 

 meter ; but it more usually occurred in irregular lumps of 

 about twelve inches in circumference and from two to four 

 inches in height. Very frequently it was covered over with 

 tufts of a small green confervoid alga, or of some sessile 

 halichondroid sponge ; and under such circumstances the red 

 colour of the polypidom was, of course, not conspicuous. The 

 crowns of tentacles, like so many stars, were of a greenish 

 colour. Some few ^lieces were found elevated on a stalk, as if 

 the budding of the original individual polyp had advanced for 

 some time in an upward and then in an outward direction. 

 The polyps were very sensitive, and quickly contracted them- 

 selves ; nor were they, like the polyps of Xenia^ at all quick 

 to show themselves after they had been once alarmed. 



My residence at Mahd after the discovery of the living 

 animals of this coral was too short to adnnr of my investigating 

 their development ; but a very casual examination showed 

 that the tubes were made up of spicules coalesced together, 

 which were found free and distinct on the u})per margin of the 

 tube, and that the tentacles Avere also thickly covered over 

 with minute pale-coloured spicules. 



As the differences between tlie species of the genus Tuhi- 

 pora are not ap])reciable without an examination of the polyps. 



