Germ layers are particularly pronounced in the vertebrates. Sponges only contain one germ layer.
Generally speaking, sponges do not have any kind of symmetry whatsoever. Sponges have asymmetry.
"Cephalization" means that the animal has a defined "head" region in which there is a lot of nervous tissue (such as the brain in humans). Sponges are not cephalized because they do not have defined head region nor do they have a central location for their nervous system.
The body cavity of sponges is large, it is open to the outside world, and it enables the sponge to consume food.
Sponges, which are in the phylum Porifera, have no segmentation. Sponges are a species of asymmetrical animals that lack distinct tissues and organs and whose body consists of two layers supported by a stiff skeleton.
Sponges don't actually have distinct resipratory, circulation, digestive or excretory systems. To feed, they filter out food particles from the water which flows through them. The particles go into the Osteia (pores) and are internally digested by Pinacocytes or Archaeocyte which partially push themselves through the wall of the Osteia.
Sponges have no true circulatory system. Instead, water is circulated by the collar cells, the rate of which can be controlled.
They do not have distinct circulatory, respiratory, digestive, and excretory systems. Instead the water flow system supports all these functions. They filter food particles out of the water flowing through them.
All types of sponges have the same excretory system. The sponges' cells absorb oxygen by diffusion from the water flow system, into which carbon dioxide and other soluble waste products such as ammonia also diffuse.
Sponges are the only multicellular animals without a nervous system. They do not have any nerve cells or sensory cells.
Sponges have three asexual methods of reproduction: after fragmentation; by budding; and by producing gemmules. Fragments of sponges may be detached by currents or waves. They use the mobility of their pinacocytes and choanocytes and reshaping of the mesosyl to re-attach themselves to a suitable surface and then rebuild themselves as small but functional sponges over the course of several days.