24 



INTRODUCTION TO CYTOLOGY 



unimportant fluid product. The term protoplast, proposed by Hanstein 

 (1880), is more appropriate and is coming into more general use, but long 

 usage and brevity have probably insured the permanence of the older 

 term. 



FIG. 1. Diagram of the cell, showing its principal constituent parts. 

 A, centrosphere, with centrosome and aster. B, nucleolus or plasmosome. C, nuclear 

 membrane. D, nucleus, filled with karyolymph. E, nuclear reticulum, composed of 

 linin and chromatin. F, plastid. G, metaplasmic inclusion. H, chondriosomes. /, 

 vacuole. /, tonoplast or vacuolar membrane. K, cytoplasm. L, ectoplast. 



Description of the Cell. The morphology of the cell will here be 

 sketched only in its barest outlines, by way of introduction to the detailed 

 descriptions presented in the subsequent chapters. 



The two most constant components of the cell (Fig. 1) are the 

 cytoplasm, in which the other cell organs are imbedded, and the 



