Pole, the name given to the extremities of the imaginary axis of the earth, round which it is conceived to revolve.
The usual gasteropod shell is in reality a hollow tube wound about an imaginary axis.
imaginary axis it is, but, acting with the panel, it nevertheless arbitrarily limits the position of all parts within the panel.
Revolving on an imaginary axis, the mass grew rounder and rounder, flattening slightly at the poles, or the ends of the axis.
Of course only one end of this imaginary axis can be above our horizon.
Purkinje noticed that the position of the imaginary axis of rotation depends on the axis around which the head revolves.
It will be noted that all the specimens figured as examples, save one, are spiral, the coils revolving about an imaginary axis.
The axis Ox is often called the real axis, and the axis Oy the imaginary axis.
The whorls of spiral univalves generally take an oblique direction in reference to the imaginary axis of the shell.
A complete turn or revolution round the imaginary axis of a spiral shell.