28 



COLLEGE ZOOLOGY 



Under the compound microscope Ameba looks like an irregular 

 colorless particle of animated jelly. The best way to obtain 

 specimens for laboratory use is to collect a mass of pond weed 

 (preferably Ceratophyllum), place it in a flat dish, and immerse 

 in water. The brown scum which appears on the surface in a 

 few days generally contains many Ameba. 



Anatomy. Two regions are distinguishable in the body of 

 Ameba, the ectosarc and the endosarc. The ectosarc (Fig. 9, 3), 



FIG. 9. Ameba protcus. i, nucleus; 2, contractile vacuole; 3, pseudopodia, 

 dotted line leads, to ectoplasm; 4, food vacuoles; 5, grains of sand. (From 

 Shipley and MacBride, after Gruber.) 



which consists of ectoplasm, is the outer colorless layer. It is 

 firmer than the endosarc and is, free from granules. The endo- 

 sarc is the large central mass of granular protoplasm. Within 

 it lies the nucleus (Fig. 9, i), which is difficult to find in living 

 Amebce, but can easily be made out in animals that have been 

 properly killed and stained. The nucleus is necessary for the 

 life of the animal, since if an individual is cut in two the part 

 with the nucleus survives, whereas the enucleated fragment dies. 



