332 ON THE INTERNAL FORM [ch. 



certain Nematodes) during division of the cell; but if the })rocess 

 be slow, more than 7 or 8 minutes long, the slow currents become 

 hard to see. Various contents of the cell are transported by these 

 currents, and clear, yolk-free polar caps and equatorial accumula- 

 tions of yolk and pigment are among the various manifestations of 

 the phenomenon. The extrusion of a polar body, at a small and 

 sharply defined region of lowered tension, is a particular case of the 

 same principle*. 



But purely chemical changes are not of necessity the fundamental 

 cause of alteration in the surface-tension of the egg, for the action 

 of electrolytes on surface-tension is now well known and easily 

 demonstrated. So, according to other views than those with which 

 we have been dealing, electrical charges are sufficient in themselves 

 to account for alterations of surface-tension, and in turn for that 

 protoplasmic streaming which, as so many investigators agree, 

 initiates the segmentation of the eggf. A great part of our difficulty 

 arises from the fact that in such a case as this the various pheno- 

 mena are so entangled and apparently concurrent that it is hard 

 to say which initiates another, and to which this or that secondary 

 phenomenon may be considered due. Of recent years the pheno- 

 menon of adsorption has been adduced (as we have already briefly 

 said) in order to account for many of the events and appearances 

 which are associated with the asymmetry, and lead towards the 

 division, of the cell. But our short discussion of this phenomenon 

 may be reserved for another chapter. 



However, we are not directly concerned here with the phenomena 

 of segmentation or cell-division in themselves, except only in so far 

 as visible changes of form are capable of easy and obvious correla- 

 tion with the play of force. The very fact of "development" 

 indicates that, while it lasts, the equihbrium of the egg is never 

 complete J. And the gist of the matter is that, if you have caryo- 

 kinetic figures developing inside the cell, that of itself indicates that 

 the dynamic system and the localised forces arising from it are in 



* J. Spek, loc. cit. pp. 108-109. 



t Cf. D'Arsonval, Relation entre la tension superficielle et certains phenomenes 

 electriques d'origine animale. Arch, de Physiol, i, pp. 460-472, 1889; Ida H. Hyde, 

 op. cit. p. 242. 



I Cf. Plateau's remarks (Statique des liquides, ii, p. 154) on the tendency towards 

 equilibrium, rather than actual equilibrium, in many of his systems of soap-films. 



