PLATE 22. 



Geodia mesotriaena var. megana Lendenfeld. 

 Figures 1-10. 



1-6. — A series of paratangential sections through a chone and the canals leading to it from the dermal 

 pores (a chonal system) ; magnified 30; phot. Zeiss, planar 20: 



1, first section, the central part in the level of the centre of the concave pore-sieve; 



2, second section, the central part half way down the ectochrotal layer overlying the sterraster- 



armour; 



3, 4, third and fourth section, in the distal and proximal part of the sterraster-armour respectively; 



5, fifth section, at the proximal limit of the sterraster-armour; 



6, sixth section, through the chone, below the sterraster-armour; 



a, dermal pores (in Fig. 1); b, oblique superficial canals leading from the pores to the chonal 

 canal (Figs. 1, 2) ; c, chonal canal (Figs. 3-6). 

 7. — Shghtly oblique paratangential section, the lower part a, a little higher than the upper part, b, 

 magnified 10; phot. Zeiss, planar 50: 

 c, chones. 



S. — The central part of the fu-st of the paratangential sections represented in Fig. 1; magnified 200; 

 phot. Zeiss, apochr. 8, compens. oc. 6. 



9. — Part of a radial section through the choanosome, showing large granular cells; azure; magnified 



750; phot. Zeiss, hom. imra. apochr. 2, compens. oc. 6: 



a, spindle-shaped granular cells, pointed at both ends; b, a granular cell, pointed at only 

 one end. 



10. — Part of a paratangential section, a transverse section through a chone; magnified 200; phot. 



Zeiss, apochr. 8, compens. oc. 6: 



a, chonal canal; b, dense mass of small asters; c, circular fibres. 



