148 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



Balfour (142) draws conclusions from F. E. Schultze's observa- 

 tions on the Embryology of Sycandra. He considers the Gastrula 

 as a colony of Protozoa, like Haeckel (143) and wishes to separate 

 the sponges from other metazoa, because the functions of Ectoderm 

 and Entoderm in the sponges are not like those in other animals. 



Lately the Analogy of the Ectoderm and Entoderm in different 

 Ccelenterata has been found to be very vague, and I have in a 

 series of papers contributed my share to the view that the Embryonic 

 layers in the higher Ccelenterata are equivalent (143a), so that the 

 fact that the Ectoderm of the sponges digests, is not sufficient 

 to warrant that the sponges really are fundamentally different 

 from all other Metozoa, and it is by no means certain, that it 

 really is the Ectoderm that digests. 



According to the late most important investigations on this 

 subject, published by Marshall (144) the whole of the inner 

 Epithelia of the sponge are entodermal, and as the digestion 

 certainly goes on within the sponge, the digestive surfaces are 

 entodermal. 



In the " Stammesgeschichte der Spongien," Zittel (144a) published 

 the classificatory system previously often alluded to, which being 

 based on Palaeontology and Zoology alike, deserves our attention. 

 He divides the Spongia into eight groups as follows : — 



1. Myxospongise. Haeckel, without skeleton. 



2. Ceratospongioe. Bronn, with horny skeleton only. 



3. Monactinellidpe Zittel, with biradiate siliceous spicules. 



4. Tetractinellidee. Marshall, with anchor- shaped spicules. 



5. Lithistidae. 0. Schmidt, with interwoven tretraradiate or 



irregular spicules. 



(142). F. Balfour. Morphology and systematic position of the Sponoidce. 

 Quart. Jour. Micr. Sc, Vol. XIX. p. 103. 



fl43). E. Haeckel. Die Gastrdatheorie Jen. Zeitschr., Vol. VIIL, p. 1. 



(143a). R. von Lendenfeld. Uber das Nervensystem der Hydroidpohjpen. 

 Z. A Band. VI. Seite, p. 69. Eucopella Campanularha. Z. f. w. Z. Band, 

 XXXVIII., S. 497. 



(144). W. Marshall. Die Ontogenie von Reniera filigra7ia. 0. Schmidt. 

 Z. f. w. Z. Band, XXXVII. Seite, 221. 



(144a). K. Zittel. Zur Stammesgeschichte der Spongien Miinchen, 187S. 



