144 On the Sponge-Fauna of Norway. 



Geodtce only those sponges which contain globates, but no 

 stellates, either in the rind or parenchyma ; it is to be feared 

 that the genus Geodia would be denuded of the majority of 

 its species if this definition were rigidly carried out. 



EXPLANATION OF THE PLATES. 



Plate VI. 



Fig. 1. Stelletta Normani, sp. now A very little larger than natural size. 

 (From a photograph.) 



Fig. 2. Transverse section ( X 2). From a photograph. 



Fig. 3. Tangential section of the muscular layer, showing the arrange- 

 ment of its fasciae : a, sphincter ; b, c, transverse section of 

 spicules. 



Fig. 4. Robust acerate spicule. 



Fig. 5. Robust simple tern ate spicule. 



Fig. 6. Bifurcated ternate spicule. 



Fig. 7. Small simple ternate spicule. 



Fig. 8. Bifurcated ternate, with a lateral spur. 



Fig. 9. Slender anchor-like ternate. 



Fig. 10. Slender ternate spicule, a variety with only two rays. 



Fig. 11. Slender acerate spicule. Figs. 4-11 are all magnified 20 

 diameters. 



Fig. 12. Cylindro-stellate spicule. 



Fig. 13. Sharp-rayed stellate.' 



Fig. 14. Trichite sheaf, mounted in Canada balsam. Figs. 12-14 are 

 multiplied 435 diameters. 



Fig. 15. Head of anchor-like ternate (x 140). 



Fig. 16. Trichite sheaf, mounted i'n glycerine, showing the divergence of 

 the trichites, which are tipped with sarcode (X 571). 



Plate VII. 



Fig. 17. Fusiform corpuscle containing nucleus and nucleolus, from the 



connective tissue of the cortex ( x i35). 

 Fig. 18. Transverse section of the cortex : a, epidermal layer, with stel- 



lates ; b, trichite layer ; c, muscular layer ; d, subcortical crypt ; 



e, ectochone ; f, layer of large granular cells (x 15). 

 Fig. 19. Axial thread of a muscle-fibre from teased-out tissue which 



has been treated with strong nitric acid and then stained 



(X435). 

 Figs. 20, 20 a. Muscle-fibres isolated after treatment with lime-water by 



teasing (x 435). 

 Fig. 21. Trichite sheaf in glycerine : a, terminal layer of sarcode, con- 

 taining nucleus and nucleolus (x 435). 

 Fig. 22. The frayed end of a teased-out bundle of muscle-fibre which 



had been treated with chromic acid ( X 435). 

 Fig. 23. Cells of the mark, surrounding a small canal (X 217). 

 Fig. 24. Wall of a large canal, showing connective tissue with fusiform 



corpuscles and scattered stellates on the exterior, and granular 



cells further in (X 217). 

 Fig. 25. Transverse section of a bundle of muscle-fibre (X 315). 

 Fig. 26. Granular ceils, with nucleus and nucleolus, from the lower face 



of the muscular layer ( X 435). 



[To be continued.] 



