30 THE BIOLOGY OF THE CELL 



gently tapping or pressing on the cover-glass, 

 thus squeezing out their contents. "What is 

 the nature of its surface? "What is its color? 

 Is the color of the cell due to the cell-wall or 

 to the cell contents ? Do you find any varia- 

 tions in color and in thickness ? Is there a 

 mouth through which particles of food may 

 enter the body ? Can you detect any especial 

 place for the absorption of fluids? Do you 

 find any organs of motion ? Is the wall at all 

 elastic ? How do you tell ? 



2. The protoplasm. — Does it entirely fill the cell ? 



"What is its color? Of what does it appear 

 to consist? Examine some which has been 

 squeezed out of the wall. 



3. The vacuole. — In what part of the cell is it 



found ? Do you ever find more than one ? Is 

 it contractile ? Of what is it composed? How 

 much of the cell does it occupy ? 



4. The nucleus. — Is the nucleus visible in every 



cell? "What is its shape? Relative size? In 

 what part of the cell is it usually found ? 



Make a drawing of a yeast cell, showing its structure 

 in detail. 



Eun a drop of magenta solution under the cover- 

 glass and note the effect on the cells. "Which stain 

 soonest and most deeply ? "What part of each ceU be- 

 comes stained, and to what extent ? On a fresh prepa- 

 ration try also one per cent, acetic acid carmine. With 

 another preparation run under the cover-glass a drop of 

 a dilute solution of Schulze's chlor-zinc iodide. 



Treat another drop of yeast with dilute potash solu- 

 tion. "What happens to the cells ? 



