These are the classic amoebae of the general biology textbooks, and
part of the intention of this collection of photomicrographs and
observations is to dispel the notion that an amoeba is a shapeless blob
of animated jelly, randomly engulfing objects it happens upon en route
to nowhere in particular.
It has been known for a long time that the general direction
of an amoeba's movement is a chemotaxic response to concentration
gradients of nutrient (and other) substances in the surrounding water,
and that most amoebae maintain a fairly definite shape, with a
recognizable front and back end, during all of their activities. They move by extending pseudopodia (Latin, false feet) which are
able to absorb food particles and which increase and decrease in size
by a process called protoplasmic streaming, which term describes it
well. Examination of individual amoebae over a period of time shows a
high level of discrimination in regard to food particles taken in. Some
are immediately absorbed, and others, apparently similar, are rejected
or avoided.
