THE CELL AND THE CELL THEORY 



controlling organ of cell activities. A distinct though delicate 

 membrane usually separates it from the surrounding cytoplasm. 

 The ground substance of the nucleus is a sort of sap, called 

 nucleoplasm, through which runs a network of thin limn fibers. 

 The most important nuclear constituent is the chromatin, a sub- 

 stance that has a strong affinity for certain dyes. Chromatin 



Attraction-sphere enclosing 

 two centrosomes 



Plasmosome or 

 true nucleolus 



rhromatin net- 

 work 



Linin network 



Karyosome, 

 net-knot, or 

 chromatin- 

 nucleolus 



FIG. 5. Diagram of a cell. (From Wilson.) 



is generally arranged in the form of a more or less irregular net- 

 work of granules which are scattered about on the linin fibers. 

 Frequently several granules unite to form a net knot or karyo- 

 some. In addition to these regular constituents of the nucleus, 

 one or more bodies, known as nudeoli, may be present. Al- 

 though cells usually contain only one nucleus, two or more may 

 occur in certain cases. 

 Cytoplasm always surrounds the nucleus. It is sometimes 



