In the ever widening hunt to understand the different aspects of sponges. We found this old blog. It discusses interesting aspects like giant sheets of single cells that cover some sponges like epidermis.
We then discovered this reference: “Glass sponges (Hexactinellida) have perhaps the most unusual body plan within the Metazoa because the majority of the tissue of the adult consists of a single giant multinucleated syncytium that forms the inner and outer layers of the sponge and is joined by cytoplasmic bridges to uninucleate cellular regions.” (Integrative and Comparative Biology Advance Access first published online on February 16, 2006)
The Inclusive Atrium 