385 Cf. Rhumbler, Arch. f. Entw. Mech. XIV, p. 401, 1902; Assheton, ibid. XXXI, pp. 46ã78, 1910.
CHAPTER VIII THE FORMS OF TISSUES OR CELL-AGGREGATES ( continued )
386 M. Robert (l. c. p. 305) has compiled a long list of cases among the molluscs and the worms, where the initial segmentation of the egg proceeds by equal or unequal division. The two cases are about equally numerous. But like many other writers, he would ascribe this equality or inequality rather to a provision for the future than to a direct effect of immediate physical causation: ãIl semble assez probable, comme on lãa dit souvent, que la plus grande taille dãun blastomû´re est liûˋe û lãimportance et au dûˋveloppement prûˋcoce des parties du corps qui doivent en naûÛtre: il y aurait lû une sorte de reflet des stades postûˋrieures du dûˋveloppement sur les premiû´res phûˋnomû´nes, ce que M. Ray Lankester appelle precocious segregation. Il faut avouer pourtant quãon est parfois assez embarrassûˋ pour assigner une cause û pareilles diffûˋrences.ã
387 The principle is well illustrated in an experiment of Sir David Brewsterãs (Trans. R.S.E. XXV, p. 111, 1869). A soap-film is drawn over the rim of a wine-glass, and then covered by a watch-glass. The film is inclined or shaken till it becomes attached to the glass covering, and it then immediately changes place, leaving its transverse position to take up that of a spherical segment extending from one side of the wine-glass to its cover, and so enclosing the same volume of air as formerly but with a great economy of surface, precisely as in the case of our spherical partition cutting off one corner of a cube.