IV] STRUCTURE OF THE CELL 199 



important forces, capillary and electrical, which play an essential 

 part in the dynamics of the cell. Even in the thickened, largely 

 soHdified cellulose wall of the plant-cell, apart from the mechanical 

 resistances which it affords, the osmotic forces developed in con- 

 nection with it are of essential importance. 



But if the cell acts, after this fashion, as a whole, each part 

 interacting of necessity with the rest, the same is certainly true 

 of the entire multicellular organism: as Schwann said of old, in 

 very precise and adequate words, "the whole organism subsists 

 only by means of the reciprocal action of the single elementary 

 parts*." 



As Wilson says again, "the physiological autonomy of the 

 individual cell falls into the background... and the apparently 

 composite character which the multicellular organism may exhibit 

 is owing to a secondary distribution of its energies among local 

 centres of actionf. ' 



It is here that the homology breaks down which is so often 

 drawn, and overdrawn, between the unicellular organism and the 

 individual* cell of the metazoonj. 



Whitman, Adam Sedgwick §, and others have lost no 

 opportunity of warning us against a too literal acceptation 

 of the cell-theory, against the view that the multicellular 

 organism is a colony (or, as Haeckel called it (in the case 

 of the plant), a "republic") of independent units of life||. 

 As Goethe said long ago, "Das lebendige ist zwar in Elemente 



* Theory of Cells, p. 191. 



f The Cell in Development, etc. p. 59; cf. pp. 388, 413.. 



J E.g. Briicke; Elementarorganismen, p. 387: "Wir miissen in der Zelle einen 

 kleinen Thierleib sehen, und diirfen die Analogien, welche zwischen ihr und den 

 kleinsten Thierformen existiren, niemals aus den Augen lassen." 



§ Whitman, C. 0., The Inadequacy of the Cell-theory, Journ. of Morphol. 

 vm, pp. 639-658, 1893; Sedgwick, A., On the Inadequacy of the Cellular Theory 

 of Development, Q.J. M.S. xxxvii, pp. 87-101, 1895, xxxviii, pp. 331-337, 1896. 

 Cf. Bourne, G. C, A Criticism of the Cell-theory; being an answer to Mr Sedgwick's 

 article, etc., ibid, xxxvm, pp. 137-174, 1896. 



II Cf. Hertwig, 0., Die Zelle und die Gewebe, 1893, p. 1; "Die Zellen, in welche 

 der Anatom die pflanzlichen und thierischen Organismen zerlegt, sind die Trager 

 der Lebensfunktionen ; sie sind, wie Virchow sich ausgedriickt hat, die 'Lebensein- 

 heiten.' Von diesem Gesichtspunkt aus betrachtet, erscheint der Gesammtlebens- 

 process eines zusammengesetzten Organismus nichts Anderes zu sein als das hochst 

 verwickelte Resultat der einzelnen Lebensprocesse seiner zahbeichen, verschieden 

 functionirenden Zellen." 



