[600] Cf. Bashforth and Adams, Theoretical Forms of Drops, etc., Cambridge, 1883.
[601] Woods, R. H., On a Physical Theorem applied to tense Membranes, Journ. of Anat. and Phys. XXVI, pp. 362–371, 1892. A similar investigation of the tensions in the uterine wall, and of the varying thickness of its muscles, was attempted by Haughton in his Animal Mechanics, pp. 151–158, 1873.
[602] This corresponds with a determination of the normal pressures (in systole) by Krohl, as being in the ratio of 1 : 6·8.
[603] Cf. Schwalbe, G., Ueber Wechselbeziehungen und ihr Einfluss auf die Gestaltung des Arteriensystem, Jen. Zeitschr. XII, p. 267, 1878, Roux, Ueber die Verzweigungen der Blutgefässen des Menschen, ibid. XII, p. 205, 1878; Ueber die Bedeutung der Ablenkung des Arterienstämmen bei der Astaufgabe, ibid. XIII, p. 301, 1879; Hess, Walter, Eine mechanisch bedingte Gesetzmässigkeit im Bau des Blutgefässsystems, A. f. Entw. Mech. XVI, p. 632, 1903; Thoma, R., Ueber die Histogenese und Histomechanik des Blutgefässsystems, 1893.
[604] Essays, etc., edited by Owen, I, p. 134, 1861.
[605] On the Functions of the Heart and Arteries, Phil. Trans. 1809, pp. 1–31, cf. 1808, pp. 164–186; Collected Works, I, pp. 511–534, 1855. The same lesson is conveyed by all such work as that of Volkmann, E. H. Weber and Poiseuille. Cf. Stephen Hales’ Statical Essays, II, Introduction: “Especially considering that they [i.e. animal Bodies] are in a manner framed of one continued Maze of innumerable Canals, in which Fluids are incessantly circulating, some with great Force and Rapidity, others with very different Degrees of rebated Velocity: Hence, etc.”
[606] “Sizes” is Owen’s editorial emendation, which seems amply justified.
[607] For a more elaborate classification, into colours cryptic, procryptic, anticryptic, apatetic, epigamic, sematic, episematic, aposematic, etc., see Poulton’s Colours of Animals (Int. Scientific Series, LXVIII), 1890; cf. also Meldola, R., Variable Protective Colouring in Insects, P.Z.S. 1873, pp. 153–162, etc.
[608] Dendy, Evolutionary Biology, p. 336, 1912.
[609] Delight in beauty is one of the pleasures of the imagination; there is no limit to its indulgence, and no end to the results which we may ascribe to its exercise. But as for the particular “standard of beauty” which the bird (for instance) admires and selects (as Darwin says in the Origin, p. 70, edit. 1884), we are very much in the dark, and we run the risk of arguing in a circle: for wellnigh all we can safely say is what Addison says (in the 412th Spectator)—that each different species “is most affected with the beauties of its own kind .... Hinc merula in nigro se oblectat nigra marito; ... hinc noctua tetram Canitiem alarum et glaucos miratur ocellos.”