194 R - S. LILLIE. 



for the existence of the localized differentiations that constitute 

 organized structure. Its physiological counterpart is seen in the 

 fact that there are constantly taking place within the single cell 

 a multiplicity of diverse and often contrary, yet simultaneous pro- 

 cesses ; these normally are so coordinated that the entire system 

 is enabled to maintain itself in equilibrium and to carry on its 

 vital functions within a certain more or less limited range of con- 

 ditions. Thus the possibility of this coordinated differentiation 

 of structure and function, which is perhaps the most distinctive 

 peculiarity of living matter, appears to depend on the above 

 properties of the colloids and on the special manner in which 

 these substances are disposed within the cell. 1 



It is, therefore, to the conditions determining the disposition and 

 state of aggregation of the colloids within the cell that we must 

 look, when we attempt to explain the mode of origin of any given 

 one of its structural features. Perhaps the most constant and 

 distinctive of these features is the division into nucleus and cyto- 

 plasm. The proteids, which are the chief colloids of these two 

 regions of the cell, are widely different in chemical nature ; this 

 implies a difference in their electrical properties, and with this is 

 probably correlated the very typical segregation which they ex- 

 hibit- -the nuclear proteids forming a central aggregate which 

 is almost always separated from the cytoplasmic proteids by a 

 distinct membrane apparently impermeable to both. This seems 

 the essential characteristic of the nucleated cell. A further 

 peculiarity of the nuclear colloids is the remarkably definite dis- 

 position which they show at times ; this is especially marked at 

 the period of cell-division, when they form arrangements and go 

 through movements of so characteristic a kind that the name 

 karyokinesis has been given to the entire process. It is this 

 peculiar mode of distribution of the nuclear colloids that I pro- 

 pose briefly to consider in the present paper : the movements 

 and grouping of the nuclear colloidal aggregates, chromatic 

 filaments and chromosomes, though apparently complex, are, 



1 For two important recent discussions of the part which colloids play in proto- 

 plasm, cf.: Hofmeister, "Die chemische Organisation derZelle," Braunschweig, Vie- 

 weg, 1901; and Pauli, " Der kolloidale Zustand und die Vorgange in der lebendigen 

 Substanz," Braunschweig, Vieweg, 1902. 



