20 THE ESSEX NATURALIST. (30.) Pearl, Raymond (1906), The movements and reactions of Fresh- water Planarians, A Study in Animal Behaviour. Q. J. Micros. Science, vol. 46, p. 509 + (31.) Ritchie, John, junr., A Contribution to the Parasitic Fauna of the West of Scotland. Glasgow Naturalist, vii. (No. 2), 1915, pp. 33- 42. (32.) Shaw, G. (1791), Description of the Hirudo viridis, a new English Leech. Trans. Linn. Soc, i., pp. 93-95, pl. vii. (33.) Southern R. (1908), Handbook of City of Dublin. Brit. Assoc. (34.) Southern, R. (1912), Clare Island Survey, Part 56, Platyhelmia. Proc. Roy. Irish Acad., xxxi. (35.) Steinmann, P. (1908), Arch. Sci. Phys. Nat., xvi., pp. 552-3. (Regeneration.) (36.) Steinmann, P. und Bresslau, E. (1913), Die Strudelwurmer (Tur- bellaria). Band 5, Monographien einheimischer Tiere. Herausgege- ben von Prof. Dr. H. E. Ziegler und Prof. Dr. R. Woltereck. (37.) Stoppenbrinck, F. (1905), Die Geschlechtsorgane der Susswasser- tricladen in normalen und in Hungerzustande, Zeitschr. fur. Wis- sensch. Zoologie, lxxix., pp. 496-547, 1 pl., 1 fig. (38.) Voigt, W. (1904), Ueber die Wanderungen der Strudelwurmer in unsern Gebirgsbaehen. Verh. naturhist. ver. d. preuss. Rheinlande, 61, pp. 496-547 (1 pl., 1 fig.) EXPLANATION OF PLATE I.