PLATE XIX. 
StrypJinus niger, 
Figure 1. Sponge, growing on Gelliodes poculum, Eidley and Dendy ; nat. size. 
2-9. Spicules — 
Fig. 2. Oxea; x 32. 
3. Dichotriaene ; x 32. 
„ 4, An oxea not proper to the sponge, 
derived from without 3 x 73. 
„ 5. Oxyaster; x 73. 
Fig. 6. Diehotriaene ; x 73. 
^ 7. The oxea of fig. 4 more highly 
magnified ; x 360. 
,, 8. Oxyaster ; x 360. 
„ 9. Amphiaster; x 430. 
10. Transverse section througli the outer part of the sponge, showing the 
absence of chones in the cortex ; x 1 5. 
11. Section showing the histology of the cortex ; x 292, 
12. Part of a section through the choanosome ; x 292. 
13. Similar to the preceding, but showing one of the darkly stained 
cells of the choanosome ; x 292. 
,, 14,15. Problematical elements from the cortex ; x 430. 
,, 16-21. Pigment cells in various stages of development ; x 430. 
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