GREEN SLIME 45 



parts or macrozoospores, or into several parts or 

 microzoospores. Note the cilia ■with which the 

 zoospores of each kind are provided. How many 

 cilia do you find on each? Are they of equal 

 length ? If the cilia are indistinct, the cells may 

 be stained with dilute iodine. Can you discover a 

 cell-wall around the protoplasm of the zoospores ? 

 Do you find that the zoospores unite? Is the 

 movement of the cells rapid or slow ? Why should 

 these reproductive cells be motile, while the veg- 

 etative cells are motionless ? Look for zoospores 

 which have come to rest. Can you determine 

 whether or not they have a cell -wall, using re- 

 agents if necessary ? Can you distinguish such a 

 zoospore from a vegetative cell? In what ways 

 do the zoospores resemble any of the Protozoa, 

 especially in structure ? Do they exhibit any ner- 

 vous properties, such as automaticity, irritability, 

 etc. ? Examine the dish of water in which the 

 zoospores were found, or transfer water contain- 

 ing them to a dish and place the dish in the sun- 

 light for a few hours, then examine a drop of 

 water taken from the side of the dish towa/rds 

 the light and another from the side away from the 

 light. "Which drop contains the greater number 

 of zoospores ? Having obtained a definite answer 

 to this question, stir the water thoroughly, so as to 

 distribute the cells evenly through it, then trans- 

 fer the dish to a place out of the direct sunlight, 

 preferably several feet from the window, and let 

 it stand for several hours. Then examine two or 

 more drops taken from opposite sides of the dish as 

 before. Do you find any difference in the position 

 of the zoospores ? If so, how do you explain it ? 



