THE NEW CELL DOCTRINE 



nated as nucleus. The living sub- 

 stance is commonly termed proto- 

 plasm. Unfortunately with the 

 progress of investigation we have 

 become more and more uncertain 

 what we can properly designate as 

 protoplasm. The nucleus is also a 

 living substance, but it is commonly 

 not reckoned as protoplasm. Many 

 authors apply the term protoplasm 

 to the body of the cell, which often 

 has a very complicated structure. 

 Thus we see spaces which we name 

 vacuoles, and which contain only 

 fluid. Such a fluid is usually not 

 considered part of the protoplasm. 

 More frequently we find special en- 

 closures, granules, etc., which reveal 



FIG. i. Two blood cells from an embryo duck. 

 The protoplasm has a uniform constitution and 

 contains the centrosome. In the rounded nucleus 

 the material is irregularly distributed and forms 

 a larger mass of chromatine. The cells have been 

 artificially colored. After M, Heidenhain. 



FIG. 2. Two plant cells 

 from the vegetative point of 

 a Phanerogam, a, younger; 

 6, older stage; k, nucleus; v, 

 sap space; cy, protoplasm. 

 After Strassburger. 



an entirely different constitution from the rest of the mass, 

 which one is inclined to name protoplasm in the stricter 



