American Museum of Natural History - Sponges (phylum Porifera) are among the simplest of animals. They have no true organs or tissues, just reproductive, feeding, and skeleton-building cells. They are hollow, taking
![Digestive cell types and tissues of choanoflagellates (a), sponges (b),... | Download Scientific Diagram Digestive cell types and tissues of choanoflagellates (a), sponges (b),... | Download Scientific Diagram](https://www.researchgate.net/publication/335024461/figure/fig4/AS:960999863640064@1606131630137/Digestive-cell-types-and-tissues-of-choanoflagellates-a-sponges-b-ctenophores-c.png)
Digestive cell types and tissues of choanoflagellates (a), sponges (b),... | Download Scientific Diagram
![Phylum Porifera: Sponges have specialized cells but no tissues; no symmetry –Sponges are the most primitive animals on Earth 570 million year old fossils. - ppt download Phylum Porifera: Sponges have specialized cells but no tissues; no symmetry –Sponges are the most primitive animals on Earth 570 million year old fossils. - ppt download](https://slideplayer.com/7479248/24/images/slide_1.jpg)