Baldwin Spencer, op. cit. pp. 24, 30-31. Not represented in Fig. 191.
Hochstetter, Morphol. Jahrb. xiii. 1888, p. 153.
The vertebral vein, which is present only on the right side, may represent the reduced anterior portion of the right posterior cardinal, as Baldwin Spencer (op. cit.) has suggested.
As an abnormality the adult Frog may retain the embryonic connexion of the right anterior abdominal vein with the heart (Buller, Journ. Anat. and Phys. iii. 1896, p. 211).
Newton Parker, Trans. Roy. Irish Acad. xxx. 1892, p. 179.