Si^onge-faima of Norway. 165 



Fig. 5. Vacuolated or vesicular connective tissue, with the gelatinous 

 matrix becoming fibrillated. X 315. 



Fir/. G. Quadritid proximal end of a trifid fork. 



Fir/. 7. A twinned spicule. 



Fir/. 8. Distal end of a spicule with fork and grapnel-ray. 



Fir/. 9. Tubercular outgrowths on distal ends of spicules. 



Fit/. 10. Bacilli : ri-c, in successive stages of development ; a, earliest 

 stage ; b, second stage ; o, adult spicule : rf and e, varieties with 

 an additional ray. 



Fi(/. 11. Connecting fibres between two globates, showing imbedded gra- 

 nular threads with nuclei. X 040. 



Fir/. 12. Cells with granides of reserve food. X 315. 



Fii/. 13. Vacuolated or vesicular tissue at the edge of an ectochone : </, 

 globate spicules, x 157. 



Plate VII. 



Tetillu cranium. 



Fii/. 1. Section through an embryo still imbedded in the maternal tissues 



(X 20). 

 Firj. 2. Section of the upper corner of a subdermal cavity (x 157). 

 Fir/. 3. Section through the entire sponge (nat. size). 

 Fig. 4. Hamate spicules enclosing nuclei ( x 040). 



Fig. 5. Ovum mtli extended pseudopodium-like processes : g, yolk- 

 granules. X 157. 

 Fig. 6. Section through a part of the sponge, showing the structure of 



the cortex, subdermal cavities, and the oscular tube (o) cut 



across (X 15). 

 Fig. 7. Poriferous membrane of fig. 15 ( x 157). The crossing lines, 



indicating fibrils, have been too heavily drawn by the engraver. 

 Fig. 8. Network forming the floor of the oscular tube (x 157). 

 Fig. 9. A node of the preceding network ( X 500). 

 Fig. 10. A trabecula of the same (X 040). 

 Fir/. 11. Axial thread of one of the fibres of the fibrous connective tissue 



(X 040). 

 Fig. 12. Young spicule in its cell from a Tetilla embryo (x 640). 

 Fig. 13. Ectoderm from the interior of a subdermal cavity ( x 040). 

 Fig. 14. Endodermic cells from the walls of a flagellated chamber 



(X 640). 

 Fir/. 15. External view of the skin, showing pores in "poriferous areas 



(X 52). 

 Fig. 10. External view of the skin, Avith its fibrous network showing 



through ; the meshes of the network are not subdivided as in 



preceding figure, but pores are still present, x 23. 

 Fig. 17. Spicule-cell surrounding a large chief spicule, drawn on same 



scale as fig. 12, to show the increase in size of the nucleus and 



nucleolus (X 640). 

 Fig. 18. Large spicule completely enclosed in spicule-cell ( x 100). 



[To be continued.] 



