1146 A MONOGRAPH OP THE AUSTRALIAN SPONGES, 



Fig. lb. — Ascetta procumbens. R. v. L. A colony on the inside of a 

 Mytilus shell. Half the natural size. Photographed from 

 a spirit specimen. The pseudopores small in the specimens 

 figured in la attain such a size in this specimen that only 

 nan-ow parts of the Sponge, consisting of one or more tubes 

 remain between the large pores. In this way the whole attains 

 the shape of a beautiful network. (Port Jackson, 10-15 fathoms. ) 



Fig. Ic. — Ascetta procumbens. R. v. L. A colony half the natural size. 

 Photographed from a spirit specimen. The reticulation extending 

 in a single plane only in the specimen figured in lb extends into 

 the third dimension and so a spongious structure is produced. 

 Attached to the sea bottom. (Off Port Jackson, 30-40 fathoms.) 



Fig. Id. —Ascetta procumbens. R. v. L A specimen similar to Ic, with 

 finer pores and different shape, growing all over the fragment of 

 a coral. 



Fig. 2. — Ascetta procumbens. R. v. L. Transverse section through a narrow 

 part of the Sponge figured in la to the right below. Osmic acid 

 Picrocarmin. The inhalent pores {P) appear in the entirely, 

 among Ascones, unprecedented shape of very long and narrow 

 canals, leading from the outer surface into the gastral cavity. 

 The tubes are cylindrical. The outer surface is smooth, only 

 the tips of the rays of a few irregulai'ly disposed spicules 

 protrude from it. The inner surface is extremely uneven and 

 covered with ridges. In the thick Mesoderm numerous ova 

 (E) are visible. A., Oc. III. 



Fig. 3. — Ascetta procumbens. R. v, L. Transverse section through part of a 

 tube. Osmic acid, Picrocarmin. The section passes through one 

 of the ridges (l) in the gastral wall and discloses a spicule and an 

 inhalent canal to view. The outer surface (a) and the inhalent 

 canals {g) are covered by a low ectodermal Epithelium, which 

 covers also several of the pi'otruding tops of the spicules (b). 

 The thick Mesoderm contains no bipolar muscular or tissue- 

 cells. The transparent gallert is filled by numerous multipolar 

 tissue-cells, the processes of which are irregularly disposed (s). 

 A young ovum {E) appears in the section. Amceboid wandering 

 cells are absent. Around the spicule CfJ the Mesoderm cells 

 form an Endothel which covers the immersed part of it. The 

 spicules are covered by a highly colourable cuticule and show 

 the axial canals very clearly. The flagellate frill cells cover the 

 whole of the inner surface of the gastral cavity. F. Oc. II. 



