Captail worms are partially segmented worms whose tails end in ornately designed cocoon-like structures. The males wave these structures around high above the seafloor in the hopes of catching the attention of females, which lack the structure. A receptive female will take a cocoon and deposit her eggs in it as the male fertilizes them. The male will then close the cocoon and bury it where the young can develop in safety.
Written by Daniel Noe, WayOutLife.com