ON THE CONDITIONS DETERMINING THE DISPO- 

 SITION OF THE CHROMATIC FILAMENTS 

 AND CHROMOSOMES IN MITOSIS. 



RALPH S. LILLIE. 

 RESEARCH ASSISTANT OF THE CARNEGIE INSTITUTION. 



Regarded from the purely physico-chemical or physiological 

 standpoint protoplasm is essentially a complex aggregate of 

 water and various colloidal and crystalloidal substances of which 

 electrolytes form a chief part. It is also important to note that 

 the distribution of the substances composing this aggregate is 

 often, perhaps always, of a highly definite and specific kind ; in 

 recognition of this fact a more or less clearly defined " structure " 

 has always been ascribed to protoplasm. Strictly speaking the 

 term " structure" must include in its significance the distribution, 

 grouping and relative positions of all the different cell-consti- 

 tuents ; ordinarily, however, we do not regard the water and the 

 more readily diffusible substances as distinctively structural ele- 

 ments ; in general we mean by such elements those whose posi- 

 tion in the complexus remains relatively constant and which give 

 the form to the whole. On this definition we observe that it is 

 primarily the colloidal substances of the cell that determine by 

 their arrangement, distribution, and state of aggregation the par- 

 ticular type of structure that is presented ; in other words, col- 

 loids form the basis of protoplasmic structure. 



The reason for this is to be sought in a consideration of the 

 general physico-chemical characteristics of this class of substances. 

 The colloids of protoplasm, by virtue of their slow diffusibility, 

 inability to penetrate one another, slow penetrability or virtual 

 impenetrability to many crystalloids, 1 and relative unliability to 

 chemical change, form throughout the cell a substratum which 

 admits of the persistence within the cell-limits of a high degree 

 of non-homogeneity. This condition is evidently indispensable 



1 Seen in the non-permeability of colloidal membranes to many dissolved sub- 

 stances. 



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