26 



FOUNDATIONS OF BIOLOGY 



we may consider its basis as consisting of a mesh work, com- 

 posed of innumerable, minute granules which permeate an 

 apparently homogeneous hyaline ground-substance. Dis- 

 tributed throughout the cytoplasm are usually various lifeless 

 inclusions such as granules of food, droplets of water or oil, 

 vacuoles of cell sap, crystals, etc., representing materials 



FIG. 8. Diagram of a cell, a-d, nucleus; a, nucleolus; 6, chromatin 

 'network'; c, linin mesh work; d, karyosome, or chromatin knot; e, meta- 

 plasmic inclusions in cytoplasmic mesh work; /, vacuole; g, plastids in 

 cytoplasm; h, centrosome, recently divided. (From Wilson.) 



which are to be, or have been, a part of the living complex, 

 or are by-products of the vital processes. This passive 

 material is frequently referred to as METAPLASM, but it is 

 quite evident that such a term stands for no essential mor- 

 phological part of the cell, and we have no absolute criterion 

 to distinguish between some granules which are regarded as 



