PLATE XXXIII. 
Pleroma turhinatum, 
Figure 1. Sponge ; nat. size. 
5 , 2. The same, showing the cut face from which the thin slices were 
prepared ; nat. size. 
3-8. Spicules — 
Fig. 3. DicliotriEene ; x 73. 
„ 4. Oxea; x 73. 
„ 6. Microxea ; x 73. The two figures 
to the right the same ; x 292. 
„ 6. Spiraster; x 73. The four 
figures vertically below this are 
examples of the same more 
highly magnified, the first three 
X 292, the last x 360. 
„ 7, 7a-7e. Rhahocrepid desmas, x 73; 
IV, the crepis, x 292. 
„ 8. The young desma at a very early 
stage; x 73. 
Fig. 8a. The same at a stage slightly 
more advanced, showing 
the crepis in the middle of 
theepirahd; x 73. 
,, %h, 8c, 8d. All young forms of 
desma; x 73. 8d'. The 
crepis as seen in 8d more 
highly magnified ; x 292. 
„ 8e. The epactine of a desma 
showing the crepis and the 
enveloping granular and 
clear layers; x 292. 
„ 8/. Two desmas, showing the 
mode of zygosis; x 73. 
9. Section at right angles to the surface, showing the general characters 
of the cortex and choanosome ; x 1 2. 
„ 10. A part of the choanosome of the preceding, more highly magnified, to 
show the characters of the chamber-system ; x 292. 
„ 11. Flagellated chambers, showing the fenestrated membrane ; x 430. 
,, 12. Two choanocytes ; x 540. 
„ 13. Part of the cortex to show its histological characters ; x 360. 
„ 14. A problematical cell from the choanosome ; x 430. 
,, 15, 15a. Sections at right angles to the surface of desmas, showing 
associated protoplasmic structures ; x 540. 
,, 156, c, d. Protoplasmic structures coating the surface of the desmas 
seen en face; x 540. 
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