XII. Contributions to the anatomy of the hirudinea

The author has investigated the following genera:— Rhyncobdellidæ.—Pontobdella, Piscicola, Clepsine, Branchellion. Gnathobdellidæ;—Aulostoma, Hœmopis, Hirudo, Hœmadipsa, Nephelis, Trocheta. The author gives a bibliography of the most important literature upon the group since the appearance of Moquin-Tandon’s monograph.External Characters and Evidences of Segmentation. The author, in attempting to answer the question—How far in the series of Hirudinean genera do external characters express the metamerically segmented nature of their organisation ?— follows in the footsteps of Gratiolet and Vaillant, who have dealt withHirudo andPontobdella respectively in this connexion. The further question— How far do such metameres represent the somites of a bristle-bearing worm ?—first suggested itself to the mind of De Quatrefages.