Page:Natural History, Mollusca.djvu/125

 a query may arise how far they assist the animal in floating upon the surface of the water.

"I again placed several of the specimens in a glass of sea-water; they were full of life, sometimes moving about, not very briskly, however, and at other times remaining floating upon the surface of the water, merely gently moving the fins. As they floated upon the surface of the water in the glass, the sides of the head, back, tail, tins, &c. exhibited at the time a light silvery blue colour, which was admirably contrasted with the deeper blue of the upper surface, and falling into the elegant pearly or silvery white of the under surface of the animal, displaying an exceedingly rich and elegant appearance. Often, when at rest, the animal would, drop one or more of the fins; but on touching them, they would be immediately raised to the former position, and that organ was turned back as if to throw off the offending object, followed at the same time by a general movement of the whole body. On touching the animal upon the back, it seemed to display more sensitiveness in that than in any other part of the body, judging from the effects produced in comparison with similar experiments on other portions of the body. For instance, the centre of the back was touched lightly and rapidly with a feather, which caused the little creature to sink, as if under the pressure of the touch, throwing at the same time the head, tail, and all the fins upwards, followed by a general distortion of the whole body of the animal. As if the gentle touch had been productive of severe pain, I invariably found every part of the upper surface of the body very sensitive when touched, displaying a general movement of uneasiness throughout the whole of the body of the creature.