1. Cell Specialization vs. True Tissues:

* Multicellular organisms have specialized cells that form true tissues - groups of similar cells working together to perform a specific function.

* Sponges have specialized cells, but they lack the organization into true tissues. Their cells are loosely organized and don't form complex structures like organs.

2. Cell Independence:

* Multicellular organisms rely heavily on the coordination and interdependence of their cells. They can't survive if separated.

* Sponge cells are relatively independent. They can live and function on their own for some time. Some sponge cells can even regenerate into a whole new sponge if separated.

3. Cell Communication:

* Multicellular organisms have complex systems for cell communication, allowing for coordinated responses.

* Sponges have more limited communication between cells, relying primarily on diffusion.

4. Embryonic Development:

* Multicellular organisms undergo a complex embryonic development with a distinct blastula stage where cells differentiate into different tissue layers.

* Sponges have a simpler embryonic development without a clear blastula stage.

Overall: While sponges are multicellular and have specialized cells, they lack the complex organization and interdependence found in true multicellular organisms. This leads many scientists to classify them as colonial organisms, a collection of independent cells that live together in a symbiotic relationship.