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

370 COLLECTIONS FROM MELANESIA.that in other species as well the distinct cloacal systems may proveto be formed in the same manner. In his latest work (Spong.Meerbus. Mexico) Schmidt says (p. 16) :— " Individuell beginnendiibernehmen in vielen Spongien die anfanglich neutralcii oder gemeiuschaftlichenGebietc die Tlolle der Individuen, aber der sich ndlirendeund fortpJlanzendeKorper ist iveder Individuum nocli ein Stocic,auch der blosse Vergleich mit Individuum und Stock passt nicht aufihn." (The italics are Prof. Schmidt's.) This view would seem tohold well, at any rate in the cases I have referred to.Parasitism.—An instance of an Oscillatorian Alga parasitic withinthe tissues of a Sponge is described under Stelletta clavosa ; a similarcircumstance has been recorded in Halisarca and /S/jo;ir/t-Z?rt (Schulze)and in a Suberite (Carter). Two examples are to be noted of theconverse case, viz. that of a Sponge constantly employing an Alga forsupport by mingling with its structures, as already noticed by Semperin Sjjongia eartilaginea, Esper, These cases are—(1) Gellius cymifonnis(v. infra), where the Sponge, though probably less in bulkthan the Alga, seems to draw the latter into its own form ; and(2) a Renierid (probably Reniera s. str.) from Port Molle, Q.uc"ensland,which coats and penetrates between the superficial fibres oftwo specimens of a species of erect arborescent Alga, giving it theappearance of the British Sponge Halicliondria albescens.A few examjiles of Sjiowiiophaga (Carter) were noticed in thebasal part of a spirit-specimen of a llhaphidopldus {R. procera) fromPort Darwin : the heads measured -005 to "01 millim., the fibreabout '001 millim. in diameter. This parasite has already beenrecorded from the Siliceous genera AxiaeUa, Gellius, Esperia, Vioa(Carter, Ann. cfeMag. N. H. (5) ii. p. 167). It also occurs in the Ceratosaof the collection ; the skeleton of a Hircinia from Torres Straitsis almost replaced by it.Geographical Distribution.1. Relations of Australia to other Districts.In attempting to compare the Australian Sponge-fauna with thefaunas of other districts, we are met by a great difficulty, caused by thevery imperfect manner in which the Ceratose and Siliceous Spongesof any given marine region, except the Northern and EquatorialAtlantic and Mediterranean, are as yet known. A paper by Prof.Sclenka (Zeitsch. wiss. Zool. xxxii. p. 467) and one by myself(Proc. Zool. Soc. 1881, p. 107)give accounts of about 30 species iromthe South Atlantic; Esper, Carter, and Vosmaer describe species fromthe Cape. The Sponges of the Pacific are almost wholly unknown*.Thanks almost exclusively to Mr. Carter's and Dr. Bowerbauk's exertions,we have a better knowledge of the Indian-Ocean fauna ; buteven this is extremely imperfect. Our more exact knowledge of thisarea (excluding Australia, for which see above, p. 366) is basedchiefly on :—* But soe Carter's (Ann. & Mag. Nat. Hist.) and Bowerbank's (Proc. Zool.Soc.) writings for sundry species from the " South Seas;" and Doderlein (Zeitsch.wiss. Zool. xl. p. G2) tor ibur new Lithistidffl from Japan.