|A diver surveying orange finger sponges on a section of Grey's Reef National Marine Sanctuary off the Georgia coast.|
|One of the uncommon freshwater sponges|
|A sponge with many oscula|
|A microscope view of silica spicules|
|The three sponge body types|
|Hexactinellid Venus's flower basket|
It is commonly assumed that sponges form what could be called an "evolutionary dead end," since there are not any animals that appear to have come from sponges. Despite this, there is some molecular evidence that suggests the sponges with calcium carbonate spicules may have given rise to other animals.
Source is Biology of the Invertebrates. Images are from Wikimedia Commons and are under a Creative Commons license or are copyright free: one, two, three, four, five, six.