CELL-LIFE AND CELL-MULTIPLICATION. 261 



an organism which it excites: an interpretation congruous 

 with the fact that the chromatin is as near to as, and indeed 

 nearer than, a nerve-ending to any minute structure stimu- 

 lated by it. 



Several confirmatory facts may be named. During the 

 intervals between cell-fissions, when growth and the usual 

 cell-activities are being carried on, the chromatin is dispersed 

 throughout the nucleus into an irregular network: thus 

 greatly increasing the surface of contact between its sub- 

 stance and the substances in which it is imbedded. As has 

 been remarked, this wide distribution furthers metabolism 

 a metabolism which in this case has, as we infer, the func- 

 tion of generating, not special matters but special motions. 

 Moreover, just as the wave of disturbance a nerve carries 

 produces an effect which is determined, not by anything 

 which is peculiar in itself, but by the peculiar nature of the 

 organ to which it is carried muscular, glandular or other; 

 so here, the waves diffused from the chromatin do not de- 

 termine the kinds of changes in the cytoplasm, but simply 

 excite it: its particular activities, whether of movement, 

 absorption, or structural excretion, being determined by its 

 constitution. And then, further, we observe a parallelism 

 between the metabolic changes in the two cases; for, on the 

 one hand, "diminished staining capacity of the chromatin 

 [implying a decreased amount of phosphorus, which gives 

 the staining capacity] occurs during a period of intense con- 

 structive activity in the cytoplasm ; " and, on the other hand, 

 in high organisms having nervous systems, the intensity of 

 nervous action is measured by the excretion of phosphates 

 by the using up of the phosphorus contained in nerve-cells. 



For thus interpreting the respective functions of chro- 

 matin and cytoplasm, yet a further reason may be given. 

 One of the earliest general steps in the evolution of the 

 Metazoa, is the differentiation of parts which act from parts 

 which make them act. The Hydrozoa show us this. In the 

 hydroid stage there are no specialized contractile organs: 

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