STUDIES ON THE COMPARATIVE ANATOMY OF SPONGES. 529 



system. /. r. Fibrous ridges on wall of oscular tube. sp. b. Bundles 

 of spicules projecting at surface. (Rather diagrammatic.) 

 Fig. 10. Part of transverse section through choanosome, X 190, showing 

 arrangement of flagellated chambers and inhalant and exhalant lacunae. 

 /. c. Flagellated chambers. 1. V . Lacunae of canal system, m. c. Meso- 

 dermal cells, probably amoeboid. At a there is an indication of a canali- 

 culus at one end of a flagellated chamber. (Rather diagrammatic.) 



Fig. 11. Separate bundle of small styli (stylodragma) from choanosome, 

 X 284. 



Fig. 12. Portion of a branched fibrous ridge from inner surface of wall 

 of oscular tube, seen in section taken parallel to the wall of the oscular 

 tube, x 284. n. Elongated nuclei. /. Flocculent granular tissue 

 covering the ridge. 



(The spicules, except where separately figured, are represented in blue.} 



