[293] A Study of Splashes, 1908, p. 38, etc.; Segmentation of a Liquid Annulus, Proc. Roy. Soc. XXX, pp. 49–60, 1880.
[294] Cf. ibid. pp. 17, 77. The same phenomenon is beautifully and continuously evident when a strong jet of water from a tap impinges on a curved surface and then shoots off it.
[295] See a Study of Splashes, p. 54.
[296] A case which we have not specially considered, but which may be found to deserve consideration in biology, is that of a cell or drop suspended in a liquid of varying density, for instance in the upper layers of a fluid (e.g. sea-water) at whose surface condensation is going on, so as to produce a steady density-gradient. In this case the normally spherical drop will be flattened into an oval form, with its maximum surface-curvature lying at the level where the densities of the drop and the surrounding liquid are just equal. The sectional outline of the drop has been shewn to be not a true oval or ellipse, but a somewhat complicated quartic curve. (Rice, Phil. Mag. Jan. 1915.)
[297] Indeed any non-isotropic stiffness, even though T remained uniform, would simulate, and be indistinguishable from, a condition of non-stiffness and non-isotropic T.
[298] A non-symmetry of T and T′ might also be capable of explanation as a result of “liquid crystallisation.” This hypothesis is referred to, in connection with the blood-corpuscles, on p. 272.
[299] The case of the snow-crystals is a particularly interesting one; for their “distribution” is in some ways analogous to what we find, for instance, among our microscopic skeletons of Radiolarians. That is to say, we may one day meet with myriads of some one particular form or species only, and another day with myriads of another; while at another time and place we may find species intermingled in inexhaustible variety. (Cf. e.g. J. Glaisher, Ill. London News, Feb. 17, 1855; Q.J.M.S. III, pp. 179–185, 1855).
[300] Cf. Bergson, Creative Evolution, p. 107: “Certain Foraminifera have not varied since the Silurian epoch. Unmoved witnesses of the innumerable revolutions that have upheaved our planet, the Lingulae are today what they were at the remotest times of the palaeozoic era.”
[301] Ray Lankester, A.M.N.H. (4), XI, p. 321, 1873.
[302] Leidy, Parasites of the Termites, J. Nat. Sci., Philadelphia, VIII, pp. 425–447, 1874–81; cf. Saville Kent’s Infusoria, II, p. 551.