PLATE XL 
Pacliastrella ahyssi, . 
Figure 1. Sponge ; nat. size. 
„ 2-23. Spicules — 
Fig. 2. Oxeaj x 49. 
„ 3, 4, 5. Calthrops ; x 49. 
„ 6. Spiraster ; x 49. 
„ 7,8. Metaster; (regarded as a variety 
of the spiraster) ; x 540. 
„ 9, 10. Spirasters ; x 540. 
„ 11-13. Microstrongyles ; x 540. 
Fig. 1 4. A young form of calthi’ops ; 
X 540. 
„ 15-23. Abnormal forms of cal- 
throps ; figs. 15, 19 
X 63; figs. 16, 18, 
20, 21 X 73; figs. 17, 
23, 22 X 95. 
24. Part of a section at right angles to the oscular surface, showing an 
excurrent canal with its oscule; x 4. The circles a and b indicate 
the parts chosen for higher magnification in figs. 25 and 26 
respectively. 
25. Part of the wall of an excurrent canal ; x 292. 
26. Part of the wall of an excurrent canal more deeply removed from the 
surface than in the preceding figure ; x 292. 
27. Granule cells occurring in a collench 5 nnatous matrix ; x 576. 
„ 28. Section of part of the choanosome, showing the chamber-system ; x 225. 
,, 29, 30. Parts of a similar section to the preceding, more highly magnified ; 
X 540. 
31. A section showing two chambers with a common aphodus ; x 360. 
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