Sponge cross section, 200x
A cross section through Scypha (Grantia?), a syconoid sponge (phylum Porifera, class Calcarea; possibly also called Sycon). The central space at the bottom is called the atrium (or spongocoel), epitheloid cells (pinacocytes) line the outside, dark-purple flagellated choanocytes line the canals that face into the atrium, and the layer between those cells is the mesohyl, which contains many different cell types. Seen at approximately 200x magnification.
Copyright © 2011 Marc Perkins