The Sipuncula, a group of ocean-dwelling worms related to annelids and mollusks, play a significant role in the bioerosion of coral reefs and are useful indicators of environmental conditions. The 155 species live in a wide variety ofmarine habitats at all depths, in sand and mud, in burrows in soft rock and dead coral, and inside such protective shelters as mollusk shells. Important food items for fish and invertebrate predators, they also recycle organic wastes and function as bioassay tools for human diseases such as cystic fibrosis and acute cholera. Edward B. Cutler brings together in...