[303] Op. cit. p. 79.
[304] Brady, Challenger Monograph, pl. XX, p. 233.
[305] That the Foraminifera not only can but do hang from the surface of the water is confirmed by the following apt quotation which I owe to Mr E. Heron-Allen: “Quand on place, comme il a été dit, le dépôt provenant du lavage des fucus dans un flacon que l’on remplit de nouvelle eau, on voit au bout d’une heure environ les animaux [Gromia dujardinii] se mettre en mouvement et commencer à grimper. Six heures après ils tapissent l’extérieur du flacon, de sorte que les plus élevés sont à trente-six ou quarante-deux millimetres du fond; le lendemain beaucoup d’entre eux, après avoir atteint le niveau du liquide, ont continué à ramper à sa surface, en se laissant pendre au-dessous comme certains mollusques gastéropodes.” (Dujardin, F., Observations nouvelles sur les prétendus céphalopodes microscopiques, Ann. des Sci. Nat. (2), III, p. 312, 1835.)
[306] Cf. Boas, Spolia Atlantica, 1886, pl. 6.
[307] This cellular pattern would seem to be related to the “cohesion figures” described by Tomlinson in various surface-films (Phil. Mag. 1861 to 1870); to the “tesselated structure” in liquids described by Professor James Thomson in 1882 (Collected Papers, p. 136); and to the tourbillons cellulaires of Prof. H. Bénard (Ann. de Chimie (7), XXIII, pp. 62–144, 1901, (8), XXIV, pp. 563–566, 1911), Rev. génér. des Sci. XI, p. 1268, 1900; cf. also E. H. Weber. (Poggend. Ann. XCIV, p. 452, 1855, etc.). The phenomenon is of great interest and various appearances have been referred to it, in biology, geology, metallurgy and even astronomy: for the flocculent clouds in the solar photosphere shew an analogous configuration. (See letters by Kerr Grant, Larmor, Wager and others, in Nature, April 16 to June 11, 1914.) In many instances, marked by strict symmetry or regularity, it is very possible that the interference of waves or ripples may play its part in the phenomenon. But in the majority of cases, it is fairly certain that localised centres of action, or of diminished tension, are present, such as might be provided by dust-particles in the case of Darling’s experiment (cf. infra, p. 590).
[308] Ueber physikalischen Eigenschaften dünner, fester Lamellen, S.B. Berlin. Akad. 1888, pp. 789, 790.
[309] Certain palaeontologists (e.g. Haeusler and Spandel) have maintained that in each family or genus the plain smooth-shelled forms are the primitive and ancient ones, and that the ribbed and otherwise ornamented shells make their appearance at later dates in the course of a definite evolution (cf. Rhumbler, Foraminiferen der Plankton-Expedition, 1911, i, p. 21). If this were true it would be of fundamental importance: but this book of mine would not deserve to be written.
[310] A Study of Splashes, p. 116.
[311] See Silliman’s Journal, II, p. 179, 1820; and cf. Plateau, op. cit. II, pp. 134, 461.
[312] The presence or absence of the contractile vacuole or vacuoles is one of the chief distinctions, in systematic zoology, between the Heliozoa and the Radiolaria. As we have seen on p. 165 (footnote), it is probably no more than a physical consequence of the different conditions of existence in fresh water and in salt.