J. P. Moore, "The Anatomy of Bdellodrilus," J. Morphol. x. 1895, p. 497.
Beddard, Trans. Roy. Soc. Edin. xxxv. 1890, p. 629, and xxxvi. 1892, p. 1.
A. G. Bourne, "On the Naidiform Oligochaeta," Quart. J. Micr. Sci. xxxii. 1891, p. 335.
F. E. Beddard, Trans. Roy. Soc. Edin. xxxvi. 1892, p. 273.
Vejdovsky, System u. Morph. d. Oligochaeten, Prag, 1884.