Earthworm embryo, ciliary band at the ventral midline (25x)
Courtesy Nikon Small World Photo Micrography Competition; Photographed by Vera Hunnekuhl
Here’s an extreme closeup of an embryonic earthworm’s developing band of cilia. Earthworms are hermaphroditic—they have both testes and ovaries and mate by swapping sperm. Afterwards, they each secrete a cocoon-forming mucus from their clitellum—the saddle-like protuberance bulging out of the top of their midsection—and deposit an egg-filled package into the ground.