The simplest type of canal system in Porifera is:

Explanation

Sponges belong to the Phylum Porifera. Ostia, spongocoel and osculum together form a canal system which is characteristic of all sponges. Canal system of Leucosolenia is of ascon type. It is the simplest type of canal system found in sponges. Water enters directly through ostia into the central spongocoel, which is lined by choanocytes, and leaves through osculum. Sycon type of canal system is found in Sycons and Leucon type is found in Spongilla. There is no canal system named as a radial type.