28 ZOOLOGY 



(c) Centrosphere. 

 {d) Cell wall. 



(Instead of regarding any particular part of the protoplasm as 

 "living" many investigators prefer to consider the life activi- 

 ties of the cell as merely the interaction of the various parts, 

 no one of which is more alive than another.) 



4. In addition to the general functions of protoplasm which 

 cells possess we need to consider in connection with cells the 

 additional functions: 



(o) Locomotion. 

 (b) Reproduction. 



5. Reproduction of cells occurs by spore formation, by 

 budding, and by division. Division of the nucleus may be 

 either direct or indirect. 



6. The following diagram, adapted from Flemming will 

 serve to represent the stages in indirect division of the nucleus : 



One mother nucleus. Two daughter nuclei, 



(o) Resting stage. Resting stage (g. \— telophase 



(6) Spireme stage. \ ^p^gpf^g^g Spireme stage, (f. ^^^ / 

 ^ (c) Astroid stage. ) ' Astroid stage (e- = anaphase. 



(d) Division of chromatin loops ^:z metaphase (d. / 



7. The important effect of this complicated process is, ap- 

 parently, to secure an equal division qualitatively and quanti- 

 tatively of the nuclear elements for the daughter cells. The 

 cytoplasmic elements in the daughter cells may be strikingly 

 unequal. 



8. The exact relations of the various structures in the cell 

 are not known. They cannot be fully understood until the 

 chemical and physical nature and interaction of living proto- 

 plasm are known. The cytoplasm, the centrosomes, and the 

 nucleus are specialized protoplasmic organs which seem to act 

 as stimuli to one another, in assimilation, growth, and division. 



