VIl] 



OF EEKERA'S LAW 



307 



of various embryos, and came to the conclusion that the mode of 

 segmentation was of httle importance as regards the final result*. 

 Lastly de Wildemanf, in a somewhat wider, but also vaguer 

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

 celhilar framework of vegetables, and also of animals, in its 

 essential features, depends 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 our former case. The three bubbles will be separated by three 

 partition surfaces, whose curvature will depend upon the relative 



Fisf. Hi. 



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

 the same dimensions ; but whether plane or curved, the three 

 partitions will meet one another at an angle of 120°, in an axial 

 line. Various pretty geometrical corollaries accompany this ar- 

 rangement. For instance, if Fig. 114 represent the three associated 

 bubbles in a plane drawn through their centres, c, c' , c" (or what 

 is the same thing, if it represent the base of three bubbles resting 

 on a plane), then the Unes uc, uc" , or sc, sc' , etc., drawn to the 



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

 Z. f. w. Z. Lv, 1893, p. 37. With this statement compare, or contrast, that of 

 Conkhn, quoted on p. 4; of. also pp. 157, 348 (footnotes). 



t de Wildeman, Etudes sur I'attache des cloisons cellulaires, Mem. Couronn. 

 de VAcad. R. de Belgique, liii, 84 pp., 1893-4. 



20—2 



