CHAPTER XIX.. Sea-Urchins.

SEA-URCHINS.

Sea Urchins in the tank--Growth of the Echinus--Its hedgehog-like spines--Suckers and pores--Ambulacral tubes--Professor Agassiz--Movements of the Echinus--Pedicellariæ--Masticatory apparatus--Common Egg Urchin--Echinus sphæra--How to remove the spines--'Do you boil your sea eggs?'--The Green-pea Urchin--The Silky-spined Urchin--The Rosy-heart Urchin, 287