PLATE XIII. 



Fig. 1. — Sphaerotylus antarcticus. Section of young specimen (x 3). 



Fig. 2. — Section of same (x 20). 



Fig. 3.— Dermal pores (x 100). 



Fig. 4. — Inner surface of cortex showing terminations of pore canals ( X 100). 



Fig. 5. — Horizontal section of papilla (x 15). 



Fig. 6. — ^Vertical longitudinal section of papilla (x 15). 



Fig. 7. — Diplodal flagellated chambers (x 400). 



Fig. 8. — Sphaerotylus capitatus (Vosmaer) choanosomal tyle (x 100) ; 8a, head of the same (x 160). 



Figs. 9, 10. — Smaller tyle and sub-tyle from spread out ends of radiating fibres of skeleton (x 160). 



Fig. 11. — Cortical tyle, also found in choanosome between the main fibres (x 100). 



Fig. 12. — Smallest kind of cortical tyle (x 100) ; 12a, the same (xl60). 



Fig. 13. — Exotyle ( x 100) ; 13a, clavate head of same (425). 



