Figure 1. Organization of the sponge body: (a) half section of a simple asconoid; (b) half section of a syconoid with slightly thickened mesohyl and folded choanoderm and pinacoderm; (c) sector of a leuconoid, with subdivided choanoderm and extensive mesohyl, traversed by a complex system of canals. (After Bergquist PR (1998) Porifera. In: Anderson DT (ed.) Invertebrate Zoology, chap. 2, p. 13. Melbourne: Oxford University Press.)

Figure 2. Stylized section of an encrusting, leuconoid sponge to illustrate the major cell types and their relationships. A, archaeocyte; BP, basopinacocytes; C, collencyte; CH, choanocyte chamber; CT, collagen tract; EC, excurrent canal; EN, endopinacocyte; EX, exopinacocyte; F, fibre; IC, incurrent canal; L, lophocyte; M, myocyte; SC, sclerocyte; S, secretory cell; SL, spicule in fibre; SP, spongocyte; ST, substrate. (After Bergquist PR (1998) Porifera. In: Anderson DT (ed.) Invertebrate Zoology, chap 2, p. 15. Melbourne: Oxford University Press.)