452 On the Sponge-fauna of Norioay. 



Fig. 4. A grapnel-spicule from the body of the sponge (X 45). 



Fig. 5. A fusiform fibre from the outer margin of a sphincter ( X 435). 



Fig. 6. Section from the skin, a short distance inwards, a, first incurrent 

 vesicle ( = ectochone) ; b, second incurrent vesicle ( = endochone 

 and subcortical crypt) ; s, a sphincter ; c, excurreut vesicle ; d, 

 d, layer characterized by food-reserve cells ; e, inner ends of a 

 tuft of spicules projecting from the skin ; /, flagellated cham- 

 bers. X 22-5. 



Figs. 7-12. Outlines of six young forms of Thenea ( X about 3), 



Fig. 13. Pauciradiate stellate or spinispirule, with the spines rounded at 

 the ends ( X 315). 



Fig. 14. Head of a form of grapnel-spicule common in the anchoring 

 tails (X 100). 



Fig. 15. Flagellated chamber, with a large cell seated, lilce a flagellated 

 cell, on the wall, but connected by a short process with a fusi- 

 form connective-tissue corpuscle: p, incurrent pore (x 250). 



Fig. 10. The inner face of the wall of a cavity, containing a sperm-ball, 

 showing its fibrillated structure and the ends of the connective- 

 tissue corpuscles which penetrate it (X 250). 



Fig. 17. Club-shaped distal end of abnormal acerate, showing a rudi- 

 mentary spine at one side ( x 100). 



Fig. 18. A young granular cell, containing a large shining grain of unde- 

 termined nature — food-reserve cell (x 500). The series of 

 changes which this kind of cell appears to undergo is represented 

 by tigs. 19, 20, 43, 45, 40, 44, 31, in the order here given. 



Fig. 19. Food-reserve cell (X 600). 



Fig. 20. A young granular spherical cell common in the gelatinous con- 

 nective tissue, and sometimes apparently forming one of the 

 cells of a flagellated chamber ( X 500). 



Fig. 21. Part of a flagellated chamber seen in optical section, with a 

 gToup of three young cells within a common cell-wall ( X 500). 



Fig. 22. Some of the spherical granular bodies which compose a sperm-ball 

 (X 600). 



Fig. 23. A flagellated chamber with a connective-tissue corpuscle ending 

 in fine processes over its wall (X 500). 



Fig. 24. Spinispirule with its nucleus ( x 500). 



Fig. 25. A thread of united connective-tissue corpuscles ; at/, the gelati- 

 nous matrix immediately surrounding a corpuscle shows a fine 

 longitudinal fibrillation ( x 333). 



Fig. 20. Food-reserve cell containing four granules (x 500). 



Fig. '27. Fibrilloe in layer surrounding a sperm-ball, having the appear- 

 ance of tails radiating from the sperm-granules, indicated by the 

 small circles (X 500). 



Fig. 28. A sperm-ball with its sm-rounding layer of modified gelatinous 

 connective tissue (X 20). 



Fig. 29. A branching connective-tissue corpuscle, having one of its fibres 

 continuous with a fusiform cell resembling a muscle-fibre : v, 

 vacuole ( X 500). 



Fig. 30. A connective-tissue corpuscle ( X 500). 



Fig. 31. A cell from the gelatinous connective tissue, consi-sting of a thin 

 wall enclosing a large vacuole-like space and a round nucleus 

 (probably an exhausted food-reserve cell) (x 500). 



Fig. 32. A small portion of the epidermis seen en face (x 500). 



Figs. 33-38. Young forms of grapnel-spicules from the roots of the young- 

 specimens indicated by figs. 7 and 8 (X 315). 



Figs. 39-42. Also young forms of grapnels, from the specimens of tigs. 

 10-12 (x' 315). 



