AMOEBA 195 
the animal flows in that direction. When this happens the 
ectosarc of the hinder portion of the body will be seen to 
wrinkle as the entosare flows away from it. 
Observe the granular nature of the entosare and the flowing 
of the granules as they move about with the motion of the 
protoplasm. Observe the food vacuoles in the entosarc; they are 
particles of food surrounded by water. Observe the pulsating 
vacuole, the organ of excretion. It will be seen to be a large 
globule of clear liquid which forms near the periphery and then 
discharges into the surrounding water. Time its pulsations; 
how many form a minute? Add a1 per cent. solution of acetic 
acid to the water and find the nucleus. 
Exercise 2. Makealargesemidiagrammatic drawing of an amoeba, 
showing the features above mentioned, and label all. 
Amoeba has no special vegetative organs except the pulsat- 
ing vacuole. Solid food consisting of plants and animals and 
particles of organic matter is ingested in the form of food 
vacuoles. These move about in the entosare with the move- 
ments of the animal’s body and the nutritive matters are digested 
and absorbed. Waste matters are then egested by being thrust 
out of a temporary opening in the ectosarc into the water. 
Respiration is carried on through the surface of the body. One 
reason for the active throwing out of pseudopodia is the neces- 
sity of increasing the relative area of the surface of the body 
for respiratory purposes. 
Reproduction in Amoeba is carried on by division. The 
nucleus first divides; the animal then elongates, and a trans- 
verse constriction appears in its middle, which is finally carried 
through the body. Two animals are thus formed, each of 
which contains half of the nucleus. As in other protozoans, 
reproduction in Amoeba is largely dependent upon nutrition. 
If the nutritive conditions surrounding them are unfavorable 
the animals gradually lose their vitality and reproductive powers 
