[62]

This view was definitely formulated by Metschnikoff in 1881 (Zool. Anz. iv. 1881, pp. 139, 153).

[63]

Cf. Morgan, J. Morphol. v. 1891, p. 445; ix. 1894, pp. 64-66.

[64]

Cf. Lang, Jena. Zeitschr. xxv. 1891, p. 1.

[65]

J. Morphol. ix. p. 72.

[66]

Mém. Mus. Paris, ii. 1815.