ON MEELIA NORMAXI. 701 



roofed over crypts wliicli had been full of calcoeytes, later macerated 

 out. X 100. 



Fig. 19. — Ground-down basal section with soft tissues remaining. 

 Thick walls of tubes as seen by strong, obliqxie reflected light, showing 

 well how vertical flanges or wings join to form walls of tubes, a. 

 Tal:)ula. x 160. 



Fig. 20. — Calcareous skeleton of Merlia on surface of carinate worm- 

 tube, macerated in Eau de Javelle, the youngest parts of skeleton being 

 lumps and scales, x 100. 



Fig. 21. — Calcareous scales on surface of worm-tulie (see fig. 20) 

 having appearance of calcified flattened cells, with a nuclear hiimp and 

 granular structure. X 425. 



Fig. 22. — A conule at base of tubercle having the appearance of a 

 petrified amoebocyte. fitting cap-like on rounded surface below, with 

 roinided basal rim and lobate basal jn-ocess, with oval nucleus and 

 granular structure. X 1500. 



PLATE 36. 



Fig. 1. — Part of mass of crypt-cells. a. An isthmus of tissue, h. 

 Flattened crypt-cells in section, much contracted, showing sections of 

 nuclei, c. Connective tissue cell. X 1000. 



Fig. 2. — Part of sponge tissue at bottom of an upper or open crypt. 

 a. Collar-cells, h. Longitudinal bundles of spicules with their sclero- 

 blasts. c. Transverse section of spicule bundle, x 1500. 



Fig. 3. — A neck or isthmus joining upper part of sponge to a mass of 

 crypt-tissue, a. Large granular crypt-cells, b. Connective-tissue cells 

 (collencytes). x 1500. 



Fig. 4.— Large granular crypt-cells. X 1500. 



Fig. 5. — Three calcoeytes on summit of a tubercle. Slightly separated 

 by pressing down cover-slip ; separation indicated by Y line. [Note. — 

 The view is in projection ; the cells extend some distance vertically 

 down.] X 2200. 



Fig. 6. — Growing edge of skeleton. Calcareous bar covered with 

 layer of calcoeytes. X 650. 



Fig. 7. — One calcocyte from those depicted in fig. 6, showing 

 granular contents (each granule with dark central spot), large oval 

 nucleus, and the nucleolus. X 4000. 



Fig. 8.— Two flattened granular cells. X 2220. 



Fig. 9. — Calcareous skeleton, showing granular appearance (due to 

 ends of fibrillse) at surface, and fibrillar structure in section, x 180O. 



Fio;. 10.— Clavidisc with its scleroblast. a. Nucleus, x 1450. 



