PLATE VIII. 
Figs. 1-8. Thenea fenestraia, . 
Figure 1. Sponge; nat. size. 
„ 2-8. Spicules — 
Fig. 2. Cladal end of anatriaene, with mesactiiial 
cladome ; x 125. 
„ 3. Cladal end of anatriaene with terminal 
cladome; x 180. 
Figs. 4-6. Plesiaster, in fig. 6 reduced to a 
microxea ; x 49. 
„ 7, 8. Spirasters ; x 292. 
Figs. 9, 10. Thenea delicuta, ..... 
„ 9. Transverse section through the sponge, from the exterior a short distance inwards ; x 49. 
„ 10. Horizontal section through the sponge in the neighbourhood of the cloaca, showing the ex- 
current canals extending up to the ectosome at a, a, though possibly they may have been 
separated from it in the complete state by the membrane, ; x 5. 
Figs. 11-20. Thenea wrightii, . ... . 
„ 11. Sponge, seen from above; nat. size. 
,, 12. The same, seen from the side; nat. size. 
,, 13-19. Spicules — 
Fig. 13. Cladal end of anatri»ne ; x 180. i fig. 15, a microcalthrops ; fig. 16, a microtriod ; 
,, 14-19. The oxyaster and its modifications ; | fig. 19, a microstyle ; x 49. 
„ 20. Flagellated chambers, showing the fenestrated membrane ; ,x 292. 
Figs. 21, 22. Thenea schmidtii, . . . . 
21. Longitudinal median section of an external bud still attached to the parent ; x 49. 
22. Longitudinal median section through a young sponge taken from the radical spicules of the 
adult, on one of which it was seated ; x 49. 
Fig. 23. Thenea sp.. 
23. Sponge; nat. size. 
Figs. 24-39. Thrombus ehallengeri, 
24. Sponge; nat. size. 
25-34. Spicules — 
Fig. 25. Plagiotrisene ; x 292. 
,, 26. The same, seen from above ; x 292. 
,, 27. Dichotrijene ; x 292. 
„ 28. The same seen from above ; x 292. 
,, 29. Plagiodi»ne, a reduction of the plagio- 
triaene; x 292. 
,, 30. Trichotriasne ; x 292. 
Eig. 31. Trichotrisene, with two cladi suppressed ; 
X 292. 
,, 32. Young form of plagiotrisene ; x 292. 
„ 33. Young form of trichotrisene, seen from 
above ; x 292. 
,, 34. Young form of dichotrisene ; x 292., 
35. Section through the ectosome ; x 292. 
36. Part of a section through the choanosome, showing the diplodal character of the chamber- 
system; X 292. 
37. Section showing a triaene spicule in situ with nuclei ranged along its sides ; x 292. 
38. Similar to the preceding, but with a scleroblast surrounding the spicule about the cladal 
origin; x 292. n 
39. Section through the choanosome, showing the general character of the canal-system : the 
canal with radiating branches is excurrent ; x 49. 
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