Canal system
Body of Scypha is organized in such a manner as to form a complex system of pores and
canals. This system is generally referred to as canal system or aquiferous system. Body wall
has essentially the same cellular layers, pinacoderm and choanoderm, with a non-cellular
gelatinous mesenchyme in between. But the body wall is so folded as to from regularly
arranged alternating invaginations and evaginations, establishing the sycon type of canal
system. Various components of canal system are as follows :
1. Ostia or dermal pores:- The external grooves of body surface are stretched over by a
thin pore membrane. It bears two or more openings for the ingress of outside water into
the body of sponge. These pores are known as ostia (L., ostium, door) or dermal pores.
Because of the presence of contractile cells or myocytes around them, the ostia can ruduce
in diameter and thus regulate the amount of ingressing water.
2. Incurrent canals:- These canals are the invaginated folds of body wall and are also
called inhalent canals. These communicate with outside through ostia but end blindly at
their inner ends. Pinacocytes line these canals throughout.