CHAPTER XIII. The Notochord and Alimentary Canal

THE NOTOCHORD AND ALIMENTARY CANAL

Relationship between notochord and gut--Position of unsegmented tube of notochord--Origin of notochord from a median groove--Its function as an accessory digestive tube--Formation of notochordal tissue in invertebrates from closed portions of the digestive tube--Digestive power of the skin of Ammocoetes--Formation of new gut in Ammocoetes at transformation--Innervation of the vertebrate gut--The three outflows of efferent nerves belonging to the organic system--The original close contiguity of the respiratory chamber to the cloaca-- The elongation of the gut--Conclusion 433