J. Coll. Japan, iv. 1891, p. 113.
Zool. Anz. xii. 1889, p. 508. This paper contains references to M. Jullien's writings on the mechanism of protrusion.
[See P. Cambridge Soc. vol. xi. Part 1, 1901.]
Zeitschr. wiss. Zool. xlvi. 1888, p. 124.
Kraepelin, Abh. Ver. Hamburg, xii. 1893, No. 2, p. 47; Braem, Bibl. Zool. (Bd. ii.) Heft 6, 1890, pp. 66 f.