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 Uttle 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 — ^Am(eba. 



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.^ The other 

 apparatus is the same as in Ex. XXII. 



Directions. — Mount some of the amoebse on a glass sUde, 

 and cover them with a cover sUp. 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 

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



