VOLVOX. 7 



4. Note the absence of color near the anterior and posterior 

 ends of the organism. Near the anterior end also notice the red 

 pigment spot, or stigma. What is its probable function? 



5. Stain a specimen with iodin and look for the nucleus. 

 It is obscured by the chlorophyl. 



Make a drawing showing all of the points observed. 

 Look through the stock cultures for other forms of Masti- 

 gophora, such as Trachelomonas, Peranema, Phacus, etc. 

 It is desirable to make drawings of the different forms. 



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 Parker and Haswell, Fig. 50.) 



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. 



