ABSTRACT
Sponges (Porifera) are a very peculiar clade. They are multicellular in that the microscopic somatic cells adhere to each other after mitosis (the haploid reproductive cells lack this property and live in the style of mobile protists) and there is also a division of labor between different cell types. The somatic cells retain a degree of freedom best illustrated by a legendary experiment. After a live sponge is pressed through a sieve, the disassociated cells reassemble into one or more viable sponges. There are neither individuals nor tissues in the metazoan sense and structural differentiation in the body is largely self-organizational.
