4 AMCEBA. 



particle of food which you may see imbedded in the body protoplasm 

 is a quantity of liquid filling what is called the food vacuole. This 

 liquid is largely water with perhaps the addition of some ferment to 

 assist in digestion. 



Under favorable circumstances, the Amoeba's method of reproduc- 

 tion by fission may sometimes be observed. Look for individuals that 

 show a constriction dividing the body approximately into halves. 



If the water in the aquarium containing the Amoeba be allowed to 

 evaporate slowly, encysted forms may also be found. In this condi- 

 tion the form of the Amoeba is more globular, the pseudopods being 

 withdrawn. Surrounding the protoplasm is a tough cell-wall or 

 cyst, from which the former will emerge to resume active life again 

 when conditions become favorable. 



A denser portion of the inner protoplasm, called the nucleus, is 



present in all Amoebae, but it cannot usually be distinguished with- 



[ put staining. Run a little methyl green, or blue, under the cover-glass 



and note results. If properly stained the nucleus will appear as a 



comparatively large mass of globular form imbedded in the endosarc. 



Exercise i. Make drawings of the Amceba at intervals, showing the 

 changes of shape. Also sketch any individuals feeding, undergoing 

 fission, or encysting. Index all the parts shown in the exercise. 



HINTS ON COLLECTING. The collector should carry several small 

 pails, filling each with the various water plants found in ponds or quiet 

 stretches of running streams. When the laboratory is reached pack 

 the contents of each pail firmly in a glass dish about 3 to 4 inches deep 

 and two or three times that in diameter. Add enough water to just 

 cover the crushed mass of plants, and cover the dish with a glass plate. 

 Label each dish with place where the material was obtained and the 

 date of starting the culture, then set it in a warm and well lighted part 

 of the laboratory. 



