1. (The page given is the one cited in the text.)
2. Lieberkuhn N . . . . . . . 1856. *Muller's Archiv p. 3.
3. Carter H. J .................. 1857. ` Annals and Mag. ' vol. 15 p. 31.
4. Kalliker A. v o n ......... 1864. «leones Histiologies) ' p. 54.
5. Schmidt O. ................ 1864. ` Suppl. der Spongien des Adriat. Meeres ' pp. 2 7