VII] OF ERR ERA'S LAW 483 



formation, tends to assume the form which would be assumed under 

 the same conditions by a Uquid fihn destitute of weight*. 



Soon afterwards Chabryf, discussing the segmentation of the 

 Ascidian egg, indicated many ways in which cells and cell-partitions 

 repeat the surface-tension phenomena of the soap-bubble. He 

 came to the conclusion that some, at least, of the embryological 

 phenomena were purely physical, and the same line of investigation 

 and thought was pursued and developed by RobertJ in connection 

 w^ith the embryology of the Mollusca. Driesch also, in a series of 

 papers, continued to draw attention to capillary phenomena in the 

 segmenting cells of various embryos, and came to the conclusion, 

 startling to the embryologists of the time, that the mode of 

 segmentation was of little importance as regards the final result §. 



Lastly de Wildeman^f, in a somewhat wider but also vaguer 

 generahsation than Errera's, declared that "The form of the cellular 

 framework of plants and also of animals depends, in its essential 

 features, upon the forces of molecular physics." 



Let us return to our problem of the arrangement of partition 

 films. When we have three bubbles in contact, instead of two as 

 in the case already considered, the phenomenon is strictly analogous 

 to the former case. The three bubbles are separated by three 

 partition surfaces, whose curvature will depend upon the relative 

 size of the spheres, and which will be plane if the latter are all of 

 equal size; but whether plane or curved, the three partitions will 

 meet one another at angles of 120°, in an axial fine. Various 

 pretty geometrical corollaries accompany this arrangement. For 

 instance, if Fig. 170 represent the three associated bubbles in a 



* There was no lack of hearty antagonism to Berthold and Errera's views. 

 Cf. (e.g.) Zimmermann, Beitr. z. Morphologie und Physiologie der Pflanzenzelle, 

 Tubingen, 1891; Jost, Vorlesungen iiber Pflanzenphysiologie, 1904, p. 329, etc.; 

 Giesenhagen, Studien iiber Zelltheilungen im Pjianzenreiohe, 1905. Cf. also K. 

 Habermehl, Die mechanische Ursache fiir die xegelmdssige Anordnung der Teilungs- 

 wdnde in Pflanzenzellen (Inaug. Diss;), Kaiserslautern, 1909. 



t L. Chabry, Embryologie des Ascidiens, J. Anat. et Physiol, xxm:, p. 266, 1887. 



X H. Robert, Embryologie des Troques, Arch, de Zool. exper. et gen. (3), x, 1892. 



§ "Dass der Furchungsmodus etwas fiir das Zukiinftige unwesentliches ist," 

 Z. /. w. Z. LV, 1893, p. 37. With this statement compare, or contrast, that of 

 Conklin, quoted on p. 5; cf. also p, 287 (footnote). 



Tl E. de Wildeman, Etudes sur I'attache des cloisons cellulaires, Mem. Couronn. 

 de VAcad. R. de Belgique, mi, 84 pp., 1893-94. 



