266 THE Microscope. 
again with tolerable regularity ; this is the contractile vesicle. 
It seems to serve two purposes first, as a pump to force water 
into and out of the body, and second, as a means of procuring 
food, for when dilated to its full extent it will sometimes con- 
tract with such vigor as to break through the ectosare and cause 
its contents to rush out into the liquid in which it les. It then 
dilates, causing a strong suction force which draws in a certain 
amount of water and with the water, infusoria, entozoa, and 
vegetal forms, the food of the amceba. 
A nucleus and nucleolus are occasionally seen. 
The first thing noticed in examining one of these little ani- 
mals is, 7¢ is contractile. Its peculiar amoeboid movements 
and its flow of protoplasm are identical in their fundamental na- 
ture with the movements occurring in a muscle during its con- 
traction. Another thing noticed is, it is irritable and automatic. 
If a foreign body be brought in contact with an amoeba when it 
is at rest, movements result. These movements are not passive 
in their nature, proportionate to the force employed, but are the 
result of an explosion of the energy of its living matter. Rarely 
does one see the amceba at rest. It is almost constantly chang- 
ing its form, not from external 
stimuli, but from changes of its 
substance, the cause of which 
lies within the body itself. The 
marked features of nervous tis- 
sue are its irritability and auto- 
matism. 
Again, it is noticed that zt zs 
secretory and excretory. Be- 
Ameceba, a, nucleus; b, foreign bodies; sides the method described 
¢, vacuole. above, the amceba has another 
way of procuring food—by extending around the object its 
pseudopodia until the particle is completely surrounded by the 
living matter. Here the foreign body remains fora time. If it be 
suitable for food it soon becomes changed into material like the 
mass surrounding it,—into “amoeba stuff.” Part of it may be 
changed and the remainder thrown off as excrementitious matter 
or the whole may be served ina similar manner. If all the par- 
ticle be not assimilated then the amoeba simply moves away by 
1 adifaea 
