Student Project Figures Figure 9 Diagram of the three different aquiferous systems in sponges, showing the evolution from the simplest body form (ascon) to the most complex (leucon) as folding of choanocytes increases. Water enters the sponge through dermal pores, passes through choanocyte chambers to excurrent canals, and exits through the osculum. Leucetta sp. has a leuconoid aquiferous system (Source: S. Degnan, pers. comm.) Figure 9