Report on the zoological collections made in the Indo-Pacific Ocean ...

426 COLLECTIONS PEOM MELANESIA.and the fibre appears to agree with Ehlers's account of the species,but I do not find the acuate spicules mentioned by hira as occurriugless abundantly than the acerates ; the size of the latter in the presentspecimens is -15 to '16 by "0055 to "007 millim. (Ehlers gives•17 millim. for the length) ; and I find (what Ehlers does not mention)fine bihamates measuring -02 by •001 to -0016 millim. But a moreextraordinary fact connected with the species is that the spongetissueis almost entirely replaced (this seems to bo the true explanationof the facts) by a ramifying and anastomosing algal fibre,•1 to •IS millim in diameter, of a semitransparent appearance andtough elastic texture in the dry state, like that of dry isinglass : thecomponent cells are about ^007 millim. in their smallest diameter.It appears to be the same species as that which forms the substratumof the mass described by Bowerbank (P. Z. S. 1876, p. 771,pi. Ixxx.) as Oplditaspongia facoich's, which is nothing more thana coating Suberitid Sponge running over the fibrous filaments ofthis same alga, which Bowerbank has taken, though not withouthesitation (see p. 772, I. c.) for the horny fibre of an OpJditispongia,although ho has identified isolated portions as alga. Inthis case also it is not until examined with the microscope that thealgal nature of most of the structure is identified with certainty.This form of s>/mhiosis has been lately noticed by Prof. K. Semperin ' Die natiirlichen Existenz-Bedingungen ' ('Animal Life,' InternationalScientific Series), where Spongia carfilaginen, Esper, is usedin illustration ; it is probably of not uncommon occurrence in theSpongida. A Formosa specimen agrees closely in the charactersboth of the sponge and alga with those from Australia. Mr. Carter(Ann. & Mag. Nat. Hist. 1878, ii. p. 163) descril)es exactly the samecircumstance in an allied species from Hong Kong, and adds othersimilar instances. Several specimens, dry and in spirit.Hub. Thursday Island, Prince of Wales Channel, Torres Straits,7-9 fms. ; Port Molle, Queensland, coral-reef.Distribution. Ceylon (Esper) ; Formosa (coll. Brit. Mas.).This species has a similar habit to G. varius, if the form may beregarded as that of the sponge and not of the alga ; but its aceratespicules are not so long and scarcely half as thick as those of thatspecies.GELLIODES, g. n.Desmacidinidoe of erect habit and well-defined form, fibre distinctand compact ; outer surface of sponge beset with pointed eminences.Spicules smooth skeleton acerate and bihamate.This genus unites the habit of Echinonemata with the fibre ofDesmacidinidfe and the spiculation of OcUius {Desmacodcs). Mr.Carter (Ann. & Mag. N. H. 1882, ix. p. 288) has referred his speciesjLros Jibnlata to the genus Phorbas, Duch. and Mich., togetherwith his Axos ancliorata, which can hardly be generically identicalwith it, as its spiculation is an acerate and an anchorate, whilePhorbas nmftrrinthus, the second species of the genus, has oidy an