The Stelleridæ are male and female, and form fertilized eggs of an orange or red colour. These eggs are first converted into a mass of cells and then into larvæ, not radiating symmetrically like their parents, but of a bilateral form, the two sides being perfectly alike and bordered by a ciliated fringe nearly throughout their whole length. These two fringes are united by a superior and inferior transverse ciliated band, and between the two the mouth is placed. A stomach, intestine, and vent are formed; the creatures can provide for themselves, and swim about as independent zooids. A young star-fish is gradually developed by a succession of internal growths, part of the original zooid is retained, and the rest is either thrown off or absorbed; then the star-fishes having lost the power of swimming, crawl slowly away and acquire their full size. There is great diversity in the external form of the zooids of the different genera, as well as in the portion of them retained in the adult star-fish. Fossil star-fishes have a very wide range. They are found among the earliest Silurian organic forms, but they scarcely bear any resemblance to existing genera. The Ophiuridæ, fished up from the bottom of the North Atlantic, come nearest to them. Five genera are found in the Oolitic formation, all extinct; three genera range from the Lias to the present seas; and five genera belonging to the Cretaceous period are represented by living species. _Echinodermata Crinoïdea._ The Crinoid Echinoderms, or Stone-Lilies, are like a tulip or lily on an upright stem, which is firmly fixed to a substance at the bottom of the sea. During the Jurassic period, miniature forests of these beautiful animals flourished on the surface of the Oolite strata, then under the ocean. Myriads of their fossil remains are entombed in the seas, and extensive strata of marble are chiefly composed of them. Their hollow joints are known in several parts of England as wheel stones, and as St. Cuthbert’s beads on the Northumbrian coast, in honour of the patron saint of Holy Island, where they abound. The Crinoïdea are of two kinds: the Encrinites, which chiefly flourished in the Palæozoic period and are now represented by a minute species (Rhizocrinus Lofotensis) lately discovered on the coast of Norway by Professor Sars, have a smooth, cylindrical, jointed stem; and the Pentacrinites, which began at the Lias, and have a five-sided jointed stem, the present representative of which is the Pentacrinus caput-Medusæ, found in the West Indian seas.