"Annelés," vol. iii. 1889-90, p. 493, in the Suites à Buffon.
Whitman quotes with regretful approval (Proc. Americ. Acad. xx. 1884-85, p. 76) Sir J. Dalyell's remark, "It does not appear that the history of the leech has advanced in proportion to the number of literati who have rendered it the subject of discussion," and adds on his own account the following severe indictment of his predecessors: "As a considerable share of the work done in this direction is purely systematic, it is somewhat surprising that not a single description of any Hirudo has been given with sufficient accuracy and completeness for a close comparison of even its more important external characters with those of other species."
"Hirudinées de l'Italie," etc., Boll. Mus. Zool. Torino, vol. ix. 1894, No. 192. See also Apathy, "Süsswasser-Hirudineen," Zool. Jahrb. Syst. iii. 1888, p. 725.
Zeitschr. f. die gesammt. Naturwiss. vi. 1872, p. 422.
But Pennant in his British Zoology has referred to a leech which is even larger. Upon the huge Basking shark (Selache) the fishermen sometimes observe a leech, which invariably drops off when the fish is brought to the surface, "of a reddish colour and about 2 feet in length"; this may be a Pontobdella.