A mi 2. mynd. Hugsanleg þróun svampa: A. Askform (Asconoid); B. Fellingaform (Syco- noid); C. Sérhæfðara fellingaform; D. Fjölgreint gangakerfi (Leuconoid). Gi, inn- streymisgangar; Gu, útstreymisgangar; Ih, innstreymishol; K, kragafrumulag; M, mið- gangur (atrial cavity); Me, miðhlaup (mesohyl); U, útstreymisop. (Teiknað eftir Hyman úr Barnes, 1980) - Possible evolution of íhe sponges: A. Asconoid type; B. Syconoid type; C. More speáalized syconoid type; D. Leuconoid type. After Hyman from Barnes (1980). 91