2014 Journal of Applied Microscopy 



of sixty-four small cells each, which develop into male gametes (spermatozoids). 

 Draw and describe free-swimming spermatozoids. 



5. Draw a colony containing female gametes (oospheres). The colony with 

 oospheres differs very little from the ordinary vegetative colony. Watch for 

 spermatozoids swarming about the female colonies. 



6. Draw and describe the ripe, red colored oospore. 



7. Note. — Eudorina shows a considerable advance in sexual development 

 over Pandorina. The female gamete (oosphere) has become stationary, but still 

 retains its flagella at first, and does not divide. The male gametes (spermatozoids) 

 are formed by the repeated division of the cells of the colony. They are very 

 small in comparison with the female cell, swim about freely in the water, and 

 have lost their chlorophyll. 



XVII. Volox globator L. Order, Protococcales. Family, Volvocaceae. 



This alga is of such size that its spherical, free-swimming body can easily be 

 seen with the naked eye. In summer or autumn it can frequently be found in 

 fresh water ponds and lakes. 



1. Take up some of the spherical colonies with a large-mouthed medicine 

 dropper or a glass tube and, having formed a little chamber on the slide with 

 a xylonite ring or with paraffin, mount and study under low power. Note the 

 rotating movements of the hollow, spherical organism. 



2. Draw a colony showing the numerous cells and some daughter colonies, 

 which appear as darker green spherical masses of various sizes. 



3. Under high power, study a single colony. About how many cells in a 

 colony of average size ? Draw a few cells, showing the cell walls, the proto- 

 plasmic strands connecting the cells (protoplasmic continuity), the chloroplast, 

 the red eye spot, the pulsating vacuole, and the two flagella of each cell. The 

 flagella will be more distinct after staining with iodine. 



4. Describe the development of a daughter colony from one of the cells of 

 the mother colony. Look for an opening (the pore) in one side of the young 

 colonies. 



5. Sexual reproduction. The colonies are hermaphrodite, developing both 

 sexual organs — the oogonia and antheridia — in late summer or autumn. Draw 

 an antheridium. This represents an enlarged cell of the colony which has divided 

 into a large number of elongated cells arranged like a bundle of asparagus shoots. 



6. Draw an oogonium, projecting into the cavity of the colony, showing the 

 enlarged oosphere. Draw a ripe oospore, showing the thick wall with peculiar 

 angular spines on the surface. 



7. Note. — In Volvox complete sexuality has been attained with the normal 

 conditions of the sexual cells (gametes). It will be noticed that the plant is 

 hermaphrodite, and this is the more usual condition in all but the higher plants. 

 Ohio State University. JOHN H. SCHAFFNER. 



