Seminiferous tubules. Light micrograph of a cross- section (Photos ... Seminiferous tubules. Light micrograph of a cross- section through seminiferous tubules in an earthworm (Lumbricus terrestris) testis. The seminiferous tubules are the site of sperm production (spermatogenesis). In the central region of each tubule are spermatozoa, formed from gametes undergoing initial meiosis and later spermiogenesis.