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Plate 24. 



Microphotographs of thick unstained preparations showing skeletal arrangement. 



Fig. 



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1. Iophon chelifer ostia-magna. From a section vertical to surface and radial to 



margin of sponge, and passing through a large 

 marginal osculum and efferent canal (cf. Fig. 4, 

 PL 20). Figure includes thickness of sponge 

 lying between surface and canal. Right margin 

 of figure represents surface of sponge; left 

 margin, canal wall; x 15. 



2. Iophon lamella. Surface; reticulate condition ; x 15. 

 3. 



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Section vertical to surface, and through entire thickness of 

 lamellate body. Right and left margins of figure repre- 

 sent surfaces of body ; x 15. 



Idem ; x 15. 



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