The Development of the Hepatic Venous System and Excretory System in Sphenodon punctatus

Abstract

Final Summary. 1 The definitive pronephros in Sphenodon extends over seven segments. Pronephric tubules (6–7) arise from the vesicular nephrotomes. Subsequently a ciliated peritoneal funnel is formed in relation to each, and the nephrotome becomes associated with a glomerulus to form a Malpighian body. The ventral border of the pronephros is covered by glomerular tissue which projects into the body-cavity and is considered to represent the fused ventral portions of the glomeruli. Abortive pronephric elements occur anteriorly to the definitive pronephros. 2 The mesonephros arises from nephrogenic tissue, and the tubules secondarily communicate with the duct. Primary, secondary, etc. tubules are formed, and corresponding Malpighian bodies. 3 The metanephros originates from a strand of nephrogenic tissue lying in association with the mesonephric duct, and extending between the posterior limit of the mesonephros and the cloaca. The metanephric duct arises as an outgrowth from the mesonephric duct. The metanephrogenic tissue originates in continuity with the mesonephrogenic tissue, and later passes dorsally to become associated with the duct primordium.