46 THE STRUCTURE OF CELLS 



Again, that frequent migration of the nucleus to the seat of 

 special metabolic activity, so often illustrated in plants, affords 

 additional indication of an exercise of the same influence. The 

 developing of a lateral outgrowth on a plant hair, one-sided 

 thickening of the cell-wall, the softening of the latter previous to 

 its perforation all these are commonly preceded by the arrival 

 of the nucleus at the part of the cell about to be affected. 



And the very facts of mitosis itself, with the profound chemical 

 and physical changes which accompany it, suffice of themselves to 

 prove that the nucleus contains substances which are capable of 

 undergoing rapid and striking changes. And indeed it is perhaps 

 not improbable that it is in that very lability characteristic of the 

 constitution of the complex substances which together make up a 

 nucleus that the supreme importance of this body to the cytoplasm, 

 and through the latter to the organism as a whole, is to be 

 attributed. 



