"02 E. XIRKPATRICK. 



PLATE 37. 



Fig. 1. — Gfowing edge of a specimen of Merlia (osmic-picro-eavniiiie 

 preparation in glycerine) showing elongated calcocytes planning o\it 

 calcareous skeleton on smooth surface of shell, a. Calcocytes. b. 

 Flagellated cliamljers and excurrent canal, c. Siliceous spicules, d. 

 Edge of sponge, e. Connective-tissue cells (coUencytes). x 750. 



Fig. 2.— CoUencytes. x 2-i25. 



Fig. 3. — Myocytes arranged radially and concentrically round a pore. 

 X 1450. 



Fig. 4.— Gland-cells, x 2425. 



PLATE 38. 



Fig. 1. — Vertical section of very young specimen figured on PL 32, 

 fig. 13. decalcified, a. Spaces left by dissolved skeleton, h. Elon- 

 gated calcocytes. c. Connective-tissue cells, with finely and abundantly 

 branched processes, d. Yoiuig wedge-shaped collar-cells, x 1000. 



Ficr. 2. — Yertical section of same showing a tylostyle and a l)undle of 

 siliceous spicules cut transversely. X 1000. 



Fig. 3. — Vertical section of same nearer to edge of sponge than in 

 fig. 1. X 540. 



Fig. 4. — Part of a collencyte (mostly cut away) showing many tufts 

 of branching processes. X 1500. 



Fig. 5. — Growing edge of a specimen. (/. Edge of sponge, b. Cal- 

 careous skeleton, x 120. 



Fig. 6. — The tuning-fork spicule from the original dried specimen 

 of Merlia. X 1050. 



Fig. 7. — Monticulipora (Heterotrypa) monilformis Nicli. 

 (from Devonian of Ontario), surface, showing polygonal network and 

 tubercles. Copied from Nicholson's * Palaeozoic Corals," "Monticuli- 

 pora," 1871, pi. i, fig. la. X 18. 



Fig. 8. — Rhaphidopora (Ch*tetes) stromatoporoides 

 Roemer. Devonian of Gerolstein. "Tangential section" (but.'' sur- 

 face view. — R.K.). From Nicholson and Foord. 'Ann. Mag. Nat. Hist.' 

 (5), xvii, pi. xvi, fig. 5. showing polygonal network. tul)ercles. and tabulae, 

 some with central hole and apparently with radial sutural lines, x 20. 



Fig. 9. — The same as fig. 8, deeper transverse section, x 20. 



