Light micrograph of the planktonic larva of the bristle worm, Eulalia viridis. The spherical body of the larva, known as a trochophore, is encircled by two or three bands of cilia used for feeding and locomotion. The bristle worms (polychaeta) are free-swimming, marine worms of the phylum Annelida (the segmented worms). Each segment of the adult bristle worm has a pair of limb-like outgrowths called parapodia, which are covered with tufts of chitinous bristles or chaetae. Magnification: x160 at 35mm size.