700 R. KIRKPATRICK. 



Fig. 4. — Transverse section o£ mass of crypt-cells (calcocytes). a. 

 Fibrilla9 of maltha, h. The same cnt across. X 540. (N.B. — Calco- 

 cytes in crypts are, for convenience, termed crypt-cells.) 



Fig. 5. — Portion of same, x 2000. 



Fig. 6. — Edge of mass of crypt-cells, showing cnt edges of surface 

 ones forming a flat epithelium (((). with the large oval nucleus forming 

 a hump on inner aspect facing cell-mass, x 1025. 



Fig. 7. — A crypt-cell showing spherical nucleus and nucleolus. X 

 3000. 



Fig. 8. — Gi'anular cell in an uppermost or open crypt, with very 

 large nucleus and nucleolus, a. ? Tokocyte (egg-cell), x 3000. 



PLATE 35. 



Fig. 1. — Tylostyles. x 525. 



Fiff. 2 



Fig. 2o. — Rhaphides. x 750. 



Fig. 3 

 Fig. 4 

 Fig. 5 



X 750. 

 Fig. 6 



filament 

 Fig. 7 

 Fig. 8 

 Fi-. 9 



-Trichodragma. x 750. 



— Clavidisc, most frequent shajDe. X 750. 



— Broken clavidisc showing axial canal, x 1000. 



— Clavidisc with narrower i-im, deeply situated in the sponge. 



Developmental form of clavidisc, with ends joined by slender 

 X 750. 

 — Incomplete clavidisc, like a sigma. X 750. 

 — Clavidisc with crossed ends, x 750. 

 — Young twisted form of clavidisc — abnormal. X 750. 

 Fig. 10. — Yery slender, simple sigmata. x 750. 



Figs. 11-15. — Abnormal spicules, all from one specimen. Fig. 11, 

 tylostyle with three knobs. Fig. 12, tylostyle with double curve. Fig. 

 18, toxa-shajDed rhaphide. Fig. 14, clavidisc with flat discs in place of 

 keyhole sinuses. Fig. 15, slender sigmata with knobs at each end. 

 All x 750. 



Fig. 16. — Calcareous skeleton, surface view, showing surface tabula, 

 with central hole, or slit, which may be quite closed. The tabula 

 show concentric circles and radial sutures radiating from centre to the 

 inter-flange suture, x 130. 



Fig. 17. — Vertical section of skeleton, showing several crypts, one 

 series being laid open and two others closed over (by vertical flanges or 

 wings). X 130. 



Fig. 18. — Base of skeleton, showing some tabula; nearly closed, whicli 



