THE AQUIFEROUS SYSTEMS OF SPONGIA-OFFICINALIS AND (CLIONA-VIRIDIS (PORIFERA) BASED ON CORROSION CAST ANALYSIS, BURLANDO, B, BAVESTRELLO G, SARA M, and Cocito Silvia , BOLLETTINO DI ZOOLOGIA, Volume 57, Number 3, DIPARTIMENTO 62032 CAMERINO, ITALY ANIMALE, UNIVERSITA CAMERINO,, p.233-239, (1990)