370 COLLECTIONS FROM MELANESIA. 



that in other species as well the distinct cloacal systems may prove 

 to be formed in the same manner. In his latest work (Spong. 

 Meerbus. Mexico) Schmidt says (p. 16): — " Individuell beginnend 

 iibernehmen in vielen Spongien die anfanglich neutralen oder gemein- 

 schaf'tlichen Grebiete die Rolle der Individuen, aher der sich nah- 

 rende und fortpjtanzende K'drper ist iveder Individuum nodi ein Stock, 

 audi der blosse Vergleich mit Individuum und Stock passt nicht auf 

 ihn." (The italics are Prof. Schmidt's.) This view would seem to 

 hold well, at any rate in the cases I have referred to. 



Parasitism. — An instance of an Oscillatorian Alga parasitic within 

 the tissues of a Sponge is described under Strlletfa chivosa ; a similar 

 circumstance has been recorded in Halisarea and Spongt lia | Schulze) 

 and in a Suberite (Carter). Two examples are to be noted of the 

 converse case, viz. that of a Sponge constantly employing an Alga for 

 support by mingling with its structures, as already noticed by Semper 

 in Spongia cartilaginea, Esper. These cases are — (1) Gellius cymv- 

 formis (v. infra), where the Sponge, though probably less in bulk 

 than the Alga, seems to draw the latter into its own form ; and 

 (2) a Eenierid (probably Reniera s. str.) from Port Molle, Queens- 

 land, which coats and penetrates between the superficial fibres of 

 two specimens of a species of erect arborescent Alga, giving it the 

 appearance of the British Sponge Haliehondria albescens. 



A few examples of Sjoongiophaga (Carter) were noticed in the 

 basal part of a spirit-specimen of a Rhapihidophlus (R. procera) from 

 Port Darwin : the heads measured -005 to *01 millim., the fibre 

 about -001 millim. in diameter. This parasite has already been 

 recorded from the Siliceous genera Aocinella, Gellius, Esperia, Vioa 

 (Carter, Ann. & Mag. N. H. (5) ii. p. 167). It also occurs in the Cera- 

 tosa of tho collection ; the skeleton of a Hircinia from Torres Straits 

 is almost replaced by it. 



Geographical Distribution. 



1. Relations of Australia to other Districts. 



In attempting to compare the Australian Sponge-fauna with the 

 faunas of other districts, we are met by a great difficulty, caused by the 

 very imperfect manner in which the Ceratose and Siliceous Sponges 

 of any given marine region, except the Northern and Equatorial 

 Atlantic and Mediterranean, are as yet known. A paper by Prof. 

 Selenka (Zeitsch. wiss. Zool. xxxii. p. 467) and one by myself 

 (Proc. Zool. Soc. 1881, p. I07)give accounts of about 30 species from 

 the South Atlantic; Esper, Carter, and Yosmaer describe species from 

 the Cape. The Sponges of the Pacific are almost wholly unknown*. 

 Thanks almost exclusively to Mr. Carter's and Dr. Bowerbank's exer- 

 tions, we have a better knowledge of the Indian-Ocean fauna ; but 

 r\ en this is extremely imperfect. Our more exact knowledge of this 

 area (excluding Australia, for which see above, p. 366) is based 

 chiefly on : — 



* But sec Carter's (Ann. & Mag. Nat. Hist.) and Bowerbank's (Proc. Zool. 

 Soe.) writings for sundry species from the "South Seas;"' and Doderlein (Zeitsoh. 

 wiss. Zool. xl. p. 62) for four new Lithistidee from Japan. 



I 



