The eyes of sea-urchins are rather highly developed, having corneæ, retinæ, and lenses. The lens generally lies in a mass of pigment, and, as Lubbock remarks, looks like a brilliant egg in a scarlet nest.[9] The eyes are scattered over the dorsal surface of the creature's body, and are commonly situated just beneath the skin; they are, however, sometimes elevated on pear-shaped bulbs. The eyes of starfish are generally quite primitive in character, as far as I have been able to determine, being simply pigmented spots which are supplied with nerves; in several species, however, I have been able to make out lenses. The eyes are arranged along the rays or arms, and vary in number. [9] "In Solaster or Asteracanthion the lenses look like brilliant eggs, each in its own scarlet nest."--LUBBOCK, _Senses, Instincts, and Intelligence of Animals_, p. 132 _et seq._ Even the stay-at-home and humble oyster has eyes (not the round, fleshy muscle called the "eye" by gourmands and epicures, but bright spots around the edge of the mantle)--primitive eyes, it is true, yet amply sufficient for the needs of a domestic, non-travelling, home body like the oyster. In most of the worms the eyes are simple ocelli--spots of pigment supplied with nerves. These eyes can discriminate between light and darkness, which is all that is required of them; but in the Alciope, a small sea-worm, these organs are brought to a high degree of perfection. This worm is exceedingly transparent, so that when observing it, it is difficult to make out more than its large orange eyes and the violet segmental organs of each ring. It looks like an animated string of violet disks surmounted by a pair of orange-colored eyeglasses. The eye of this creature is strikingly like that of a human being; it has a cornea, an "eye-skin," a lens, vitreous humor (posterior chamber), and retina.