VOL VOX. 9 



VOLVOX. 



Volvox globator is better for study than V. aurens. It may 

 be distinguished from the latter by the larger size of the colony, 

 the greater number of cells that compose it (about 15,000), the 

 angular shape of the individual cells, and the stout connecting 

 processes of protoplasm, into which chromatophores may enter. 



Observe the movements of colonies in a watch-glass of water, 

 with the naked eye and with a low power of the microscope. 



1. Do the colonies tend to collect toward a particular side 

 of the dish? What reason is there for the reaction? 



2. Place a number of colonies on a slide with enough water 

 to allow them to be covered without crushing them. Study 

 first with the low and then with the high power and determine 

 the species. Understand the relation of the individual cells to 

 the colony. (See Doflein, p. 240.) 



Draw a figure showing several cells and their protoplasmic con- 

 nections. 



3. Compare in detail an individual cell with Euglena. 



4. Observe, if possible, certain cells, called parthenogonidia, 

 which are specialized for asexual reproduction. These divide and 

 form the daughter colonies, which become detached and swim 

 in the interior of the parent colony. They are finally liberated 

 by the rupture of the wall of the parent colony. 



Make a figure of a parent colony that incloses several daughter 

 colonies of different sizes. 



5. V. globator is monoecious. Look for macrogametes and 

 bundles of microgametes. 



Figure them. 



6. Be sure to recognize the significance of the fact that the 

 cells of Volvox are differentiated into somatic and germ cells, 

 and to understand the resulting physiological division of labor. 

 (Calkins, Protozoa, p. 232.) 



7. Consider the reasons for and against regarding Volvox 

 and allied organisms as animals rather than plants. 



Meyer: Ueber den Bau von V. aurens and V. globator. Bot. Cent., 63, 

 1895, 



