429 Mummery, J. H., On Calcification in Enamel and Dentine, Phil. Trans. CCV (B), pp. 95〓111, 1914.

430 The artificial concretion represented in Fig. 202 is identical in appearance with the concretions found in the kidney of Nautilus, as figured by Willey (Zoological Results, p. lxxvi, Fig. 2, 1902).

431 Cf. Taylor〙s Chemistry of Colloids, p. 18, etc., 1915.

432 This rule, undreamed of by Errera, supports and justifies the cardinal assumption (of which we have had so much to say in discussing the forms of cells and tissues) that the incipient cell-wall behaves as, and indeed actually is, a liquid film (cf. p. 306).