And a similar argument might apply to the small but whole blastula of echinus, and to all other cases.
Then coasting along the shore 100 stadia, we find above it, echinus.
It cannot be our task to follow all the points of organogenesis of echinus in detail.
The projection of the echinus beyond the fillet of the abacus should be equal to the size of the eye.
echinus sphra is the most common on the Norfolk coast; E. miliaris, a small species, is also very abundant about Cromer.
When a perpendicular surface is reached, the echinus may either ascend it or not, as in the case of the Star-fish.
A name in our northern isles for the sea-urchin, echinus marinus.
Several interesting questions arise with reference to these righting movements of echinus.
This is sometimes done, which proves that the energy required to perform the feat is not more than a healthy echinus can expend.
Nerve-cells lying among the muscular fibres at the base of a spine in echinus.