236 APPENDIX 



strips of paper properly wound inside to represent the chromatophore, 

 and some object suspended in the center to illustrate the position of the 

 nucleus. A simple model of this character made with the cooperation of 

 the class will greatly assist the students to a clear understanding of the 

 study outlined in Sec. 56. 



Whenever possible, a study of the Amoeba or Euglena in comparison 

 with the cell of Spirogyra will be found very helpful in making clear 

 the characteristics of a protoplast. 



Stained preparations of Spirogyra filaments (Sec. 211) may help to 

 an understanding of the cell structure, but in general it is better that 

 the student handle living material and with the aid of a few simple re- 

 agents (such as iodine and the salt solution) discover the facts for 

 himself. 



7. Cultures of Amoeba. Cultures of Amceba may be made in an aqua- 

 rium jar overstocked with filamentous algse. Introduce sediment from 

 a pool of Oscillatoria with a mass of the algse ; growths of Scenedesmus 

 are also likely to have Amcebm. Place the jar near a window but just 

 out of the direct rays of the sun. The filamentous algse will decay and 

 after a few weeks a coating will be formed on the sides of the jar. 

 From this coating or from the sediment on the bottom of the jar 

 Amoebce can usually be obtained in quantity. They are generally most 

 abundant on the sides nearest the light. In preparing material for the 

 class gather a quantity of the sUme and sediment with a pipette and 

 place in a small bottle. After a few hours the water at the top will 

 frequently contain so many Amcebm that the students may readily find 

 them in mounted drops. 



8. Nuclear and cell division. Nuclear and cell division may also be 

 studied from preparations of the pollen mother cells of the lily (Sec. 141) 

 and in sections of various growing tissues such as stem tips, developing 

 ovules, embryo sacs of lily, etc. 



9. Cultures of Euglena. A culture of Euglena in a shallow dish with 

 leaves and sediment at the bottom may be allowed to slowly dry up by 

 evaporation. The Euglence will pass into the encysted condition. This 

 dish of dried material may then be placed aside and will keep indefi- 

 nitely. If water be added, the encysted Euglence will come forth again 

 in the motile condition. 



10. Sphaerella and VoItox. If stones are placed in a dish swarming 

 with Sphmrella, the motile cells will settle upon them and pass into a 



