Cross section through the branchiogenital region of the male Lancelet Branchiostoma. A: Myomere, B: Notochord, C: Nerve cord, D: Epibranchial groove, E: Endostyle, F: Intestine, G: Pharangeal cavity, H: Gill bar, I: Atrium, J: Testes, K: Metapleural fold.