28 ZOOLOGY 



(c) Centrosome. 



(d) Cell wall. 



4. In addition to the general functions of protoplasm which 

 cells possess we need to consider in connection with cells the 

 additional functions : 



(a) Locomotion. 

 (6) Reproduction. 



5. Reproduction of cells occurs by fragmentation, by 

 budding, and by division. Division may be either direct or 

 indirect. 



6. The following diagram, adapted from Flemming will 

 serve to represent the stages in indirect division: 



One mother nucleus. Two daughter nuclei 



(a) Resting stage. Resting st 



(&) Coil stage. 1 =prophase Coil stage (f. 



) Astroid stage. ) Astroid stage (e. 



(d) Division of chromatin loops = metaphase (d. / 



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

 parently, to secure an equal division 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 understood until the chemical 

 and physical nature of living protoplasm is known. The 

 cytoplasm, the centrosomes, and the nucleus seem to act as 

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



