Page:The fairy tales of science.djvu/124

96 natural state, but when exposed to light, its skin gradually becomes darker, and at last assumes an olive tint. Its nasal organs appear large; and it is abundantly furnished with teeth, from which it may be concluded that it is an animal of prey, yet in its confined state it has never been known to eat, though it has been kept alive for many years by occasionally changing the water in which it was placed." This strange creature, whose life is passed in total darkness, has long been a puzzle to philosophers, as all the facts revealed by science go to prove that light is indispensable to organization.

The dependence of animal life upon light is beautifully exhibited in the ocean. Water is not absolutely translucent, and it has been calculated that light must lose all its influence at the depth of a very few hundred feet into the ocean, even under the tropics. Now, it has been satisfactorily proved by an extensive series of dredging experiments that life diminishes as we descend into the ocean, and that beyond the depth of three hundred fathoms it ceases altogether. But this is not all, for besides being much more numerous, the shells of the different mollusca are much more brightly coloured in the upper regions of the ocean than in the lower, in fact, a regular gradation of tints may be traced as the shells grow deeper in hue as they approach the light.

Man himself is highly susceptible to the influence of light, and pines and sickens in darkness.