SPONG1A. 



75 



gaps, and riddled with air-cells. This tissue is formed of delicate 

 flexible fibres, uniting in all directions by anastomosis, but presenting 

 numerous pores, which are formed by what is termed osculation, 



Fig. 10. Spongia, half the natural size, attached to its rocky bed. 



having irregular conduits which connect them. In this tissue certain 

 very small solid bodies are discovered, named spiculse. The spiculse 

 are siliceous or calcareous in their nature, varying according to the 



