Vincent, Trans. Zool. Soc. xiv. Part iii. 1897, p. 41. For bibliography see Vincent, Internat. Monatsschr. f. Anat. u. Phys. xv. 1898, p. 319.
Giacomini, quoted by Swale Vincent, Journ. Anat. and Phys. xxxviii. 1903, p. 41.
Vincent, op. cit. pp. 32, 33.
Balfour, Quart. J. Micr. Sci. xxii. 1882, p. 12.
Swale Vincent, op. cit. p. 78.