240 



PRACTICAL ZOOLOGY 



specialized kind of protoplasm; it is sometimes called nucleo- 

 plasm to distinguish it from the rest of the protoplasm, which 

 is designated cytoplasm. 



PROTOPLASM THE PHYSICAL BASIS OF LIFE. - - Protoplasm is 

 known as the physical basis of life since every organism, whether 



p 



.-,7.'>: - :'"' " /&*:**-'' :-..:'v,. ; 



- " . - , - " '' ' ' ' ' 





' 1*3 *w ;\i/.*v'.- -*., . . 



V# ; <8tf. ;< * 



. v. * . ^ o :kir*r 



<3 

 <& 



?^^^.^ 



-m e 



FIG. 130. Diagram of a typical cell. 



as, astrosphere ; e, centrosome; ch, chromatin; cr, chromidia; ec, ecto- 

 plasm ; en, entoderm ; k, karyosome ; 1, linin ; m, mitochondria ; me, meta- 

 plasm ; nm, nuclear membrane; p, plastid ; pi, plasmosome or nucleolus; 

 s, cytoplasm; v, vacuole. 



plant or animal, has this substance as a basis. We should there- 

 fore know something more about it. Ameba (Fig. 133) consists 

 of naked protoplasm. The outer layer is very clear, and rather 

 firm like stiff jelly; the inner mass is granular and more watery. 

 The activities of Ameba are those of animals in general, but in 

 the Metazoa these activities are distributed among many cells, a 

 condition known as division of labor among cells or specializa- 

 tion. 



