THE CELL 



and nuclear division (Fig. 

 7, and see Figs. 34 and 

 137). The cytoplasm is the 

 vegetative part of the cell . - ,, 

 and is frequently charged 

 with 'foodstuffs, such as 

 yolk granules and starch, 

 and with secretion and 

 excretion products (Figs. 

 8 and 9). Plastids and 

 chloroplasts are found most 

 frequently in plant cells 

 (Fig. 10). Vacuoles con- 

 taining fluids are frequently 

 found in animal cells and 

 are always present in a 

 mature plant cell. Within 

 the vacuoles, crystals and 



Other Solids are Sometimes 



. . . ' 



Stored (see rig. 9)- 



A Very important StrUC- 

 . .. , 



ture is sometimes found 



ncl. 



G- 8 " Gland cell from leech, Pisicola. sec., secreted ma- 

 terials in various stages of elaboration ; ncl., nucleolus; 

 , nucleus ;cy/.c/t.,cytoplasmic channels containing and 

 delivering the secretion granules to the large distal vacu- 

 ole; di.tu., discharging tubes of this and two other cells. 



in the cytoplasm as a permanent feature; sometimes it is but a tem- 

 porary structure, arising de novo, and in other cases it may be absent. 



FIG. 9. Section through parts of two regions of lobster's nephridium. ex.p., excretory 

 products; ex.-v., excretory vacuoles. X 425. 



