38 EXPERIMENTAL PHYSIOLOGY 



nucleus? Make a drawing of what you see and label in such 

 a way as to answer the above questions. 



Now add a little of the normal salt solution, to be run 

 under the cover glass, and examine with the high power. Do 

 you see any nucleus now? any protoplasm? What has hap- 

 pened to the protoplasm? Draw and label such parts of 

 the cell as show. A little methyl green or Delafield's hsem- 

 atoxylin added will make the nucleus more distinct. 



Make a list of the differences and similarities between the 

 cells examined in Ex. XXII and Ex. XXIII. 



NOTE. The comparison of cells should be further demonstrated 

 with other materials by the instructor, until the essential and varia- 

 ble components are clearly grasped by the pupil. Some suggested 

 material: Pleurococcus, potato, diatoms, root tips, etc. 



XXIV. STUDY OF LIVING PROTOPLASM AMCEBA. 



Apparatus. About a month beforehand collect the leaves and 

 sediment from pools of still, but clear water. Distribute this mate- 

 rial together with a few water plants (Nitella or Chara) in sev- 

 eral open, shallow dishes. Keep covered with water. When, in 

 course of time, the water in these has become clear and free from 

 scum, take up with a pipette (medicine dropper) some of the sedi- 

 ment from the very surface of the leaves. Examine this for amoebae 

 with the low power (two-thirds objective). When the dish contain- 

 ing them in quantity is located, mark this for supply. 1 The other 

 apparatus is the same as in Ex. XXII. 



Directions. Mount some of the amoebae on a glass slide, 

 and cover them with a cover slip. Locate one of the animals 



*A. W. Weysse of Boston University gives in "Science," Vol. XX, No. 515, 

 the following method of securing amoeba. Collect a considerable number 

 of lily pads. Remove with a spatula the slime which adheres to the lower 

 surface and put it in a shallow glass aquarium containing water six or eight 

 centimeters deep. Place the vessel near a window and in a week or two 

 amosbae will be abundant on the surface of the sediment at the bottom. 



