VIU INTBODTTCTION. 



first stages of development in special capsules or in the canals of the mother. 

 It develops into a ciliated gastrula, which leaves the body of the mother and 

 swims about freely on its own account for some time. Finally the embryo 

 attaches itself to a suitable surface, loses its regular shape, and grows out to 

 form a sponge. We know little about the later stages of development, and 

 I recommend them to the special attention of students. 



The digestive functions of Sponges are carried on in an unknown manner. 

 We do not even know what Sponges feed on. Their organization precludes 

 the possibility of their devouring things of a large size, and I am inclined 

 to believe that their noui'ishment consists of the organic substances contained 

 in solution in the water which passes through their elaborate and complicated 

 canal-system. I should like to draw the attention of students to this point 

 also. 



Sponges are met with both in fresh water and in the sea. The freshwater 

 forms are few in number, and the Australian freshwater Sponges are very 

 similar to the European. The diversity of marine forms is very great, and it 

 appears that the Australian coast is particularly rich in Sponges. 



The systematic position of Sponges has been extensively discussed, and 

 many different views ha\e been put forward with regard to it. I think, 

 however, that my publications on the subject* may be regarded as fairly 

 establishing the fact that Sponges are Metazoa and not Protozoa, and that 

 they belong to the Grade Coelentera, and do not form a separate group equiva- 

 lent to the groups Metazoa and Protozoa. Within the Grade Coelentera I 

 distinguish two Phyla : — (1) Mesodernialia, the chief organs of which are 

 mesodermal in origin ; and (2) Epithelaria, the chief organs of which are 

 epithelial (ectodermal and entodermal) in origin. The Mesodermalia comprise 

 the Sponges, and the Epitlielaria comprise the Hydromedusse, Scyphomedusse, 

 Anthozoa, and Ctenophora, 



The classification of Sponges is at present in some confusion, as every author 

 establishes a different system, and no time is allowed to verify them before 

 another new system crops up. I shall here of course follow the system 

 established by myself. Time will show whether my system or another 

 is correct ; but I rather suspect that none of them will be found quite 

 satisfactory. The system here employed differs somewhat from that published 

 by me in the ' Proceedings of the Zoological Society ' for 1886. 



After this short Introduction I now enter on my proper subject — the 

 descriptions of the Sponges which were in the Australian Museum at the 

 beginning of 1886. This work is simply a descriptive Catalogue, and I do 

 not wish to have it considered in any other light. 



* Prop. Zool. Soe. 1886 ; Zoo]. Jahrb. vol. ii. 



