41. The Development of the Kidney in Ampullaria (Pila) gigas



  • 1The right kidney and left kidney in the embryo arise as evaginations of the pericardium. Mesodermal cells from the neighbourhood adhere to these evaginations.
  • 2While the left kidney disappears, the right kidney enlarges and comes into contact with the invagination of the ectoderm which later forms the mantle-cavity in the posterior region.
  • 3The right kidney then opens into the mantle-cavity.
  • 4That portion of the mantle-cavity with which the kidney comes into contact becomes a tubular organ distinct from the mantle-cavity, and is called the “ureter.”
  • 5As a result of torsion, the right kidney of the embryo becomes the left, posterior kidney of the adult.
  • 6The ureter becomes dorsal and lies anterior to the left, posterior kidney. It becomes the anterior kidney of the adult.
  • 7In the adult the glandular posterior kidney, which opens internally into the pericardium, discharges its products into the anterior kidney, and thence to the exterior.
  • 8The anterior kidney of the adult Ampullaría is a modified and enlarged ureter, homologous with the ureter of Vivipara.