With a cast of characters so strange and bizarre that it would be the envy of any science fiction movie producer, the invertebrates—animals with no backbones—dominate the marine environment of the Pacific Northwest in terms of both diversity and total population. The fact that in a majority of species the tiny planktonic young bear little if any resemblance to the more recognizable adults further increases the seemingly endless array of unbelievable life designs. Most invertebrates are intimately associated with the sea floor or other submerged substrates for most of their lives, but spineless creatures frequent virtually every available space of the marine habitat that is our coast. This overwhelming assemblage of spectacular creatures may be biologically—though not necessarily easily—segregated into a number of phyla (singular: phylum).