PLATE 25. 



Geodia mesotriaena var. megana Lendenfeld. 

 Figures 1-11. 



1. — Radial section through the outer, ectochrotal layer of the cortex; magnified 100; phot.. Zeiss, 



apochr. 16, compens. oc. 6: 



a, surface of the sponge; b, distal, freely projecting ends of the small dermal rhabds: c, 

 oblique superficial canals ; d, radial tufts of small dermal amphioxes; e, sterraster-armour. 



2, 3. — Sterraster; magnified 300; u. v. phot., Zeiss, q. monochr. 1.7: 



2, focused higher; 3, focused lower. 



4. — Sterraster; magnified 300; phot., Zeiss, apochr. 4, compens. oc. 6. 



5. — Group of sterrasters in a spicule-preparation ; magnified 150; phot., Zeiss, apochr. 8, compens. oc. 4. 

 6,7. — The umbilicus and the adjacent parts of the surface of two sterrasters; magnified 1800; u. v. 



phot., Zeiss, cj. monochr. 1.7, q. oc. 10. 

 8. — Surface of a sterraster opposite the umbilicus; magnified 1800; u. v. phot. Zeiss, q. monochr. 1.7, 

 q. oc. 10. 



9-11. — The umbilicus of a sterraster and the adjacent parts of the surface; magnified 1200; u. v. phot., 

 Zeiss, q. monochr. 2.5, q. oc. 10: 

 9, focused near the bottom of the umbilical pit; 10, focused halfway up the umbilical pit; 

 11, focused on the surface round the umbilical pit. 



