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Even in this modified chordaea-theory the six fundamental organs of the chordula would retain their great value. The medullary tube would be originally a chemical sensory organ, a dorsal olfactory tube, taking in respiratory-water and food by the neuroporus in front and conveying them by the neurenteric canal into the primitive gut.
Naturally, I do not mean that the Vertebrates have descended from the Tunicates, but that the two groups have sprung from a common root. The chordaea-theory received the most valuable and competent support from Carl Gegenbaur.
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