The various colored lights seen upon certain crustaceans and worms, and their peculiar position, point to the possible belief that they may be signals, constituting a primitive means of communication; also of use to the animals in lighting their way, as we have seen in the case of the pyrophorus. The lights of fishes, whatever may have been the object of nature, serve several distinct purposes: to draw the attention of enemies, to attract prey, and to illumine the gloom about them. Any one who has fished at night by torchlight well knows the attraction that light has for fishes of all kinds, and when submarine electric lights have been watched, groups of fishes and squids have been observed about them; so it is evident that predatory fishes possessing lights have in their lure a decided advantage. Actual experiment has shown that the electric light can be seen ninety-nine feet under water. The soft rays of animal phosphorescence would not penetrate so far, but would be powerful enough to illumine the water for some distance about them. The deep-sea fishes which are not remarkable for their phosphorescence, or do not possess it at all, have feelers in many instances, and grope about like blind men: while others have eyes that not only see, but are possible emitters of light themselves. In the case of the predatory shark captured by Bennett, we may assume that the light was an effective lure: but the same will not apply to the brilliant scopelus and other delicate little creatures almost completely defenceless; so that it will be seen that it is as difficult to lay down fixed rules for the use of the light as to explain the cause of its production. The phosphorescence of corals and their allies,--gorgonias, sea-anemones, etc., may serve to attract prey. The minute crustaceans, so valuable to food fishes, are by their unfortunate gift rendered visible to their enemies, and the same may apply to many of the worms; while in a certain species of the genus _Polynæ_, we have seen that the phosphorescent scales which it throws off may be used to delude its enemies, just as when certain lizards cast off their tails, and dart away, leaving them wriggling and squirming, to attract the attention of their pursuers. Certain crustaceans have luminous bands or spots which undoubtedly serve as lanterns, while many have eyes that are modified into light-emitting organs. The light produced inadvertently by schools of mackerel, in their movements through water teeming with phosphorescent animals, redounds to the benefit of the fishermen. The pale phosphoric cloud, seen from the top masthead, resting upon the surface of the ocean, tells the secret of their exact situation; and, by surrounding it with the great net, large schools are often caught. [Illustration: PLATE XXV. LUMINOUS WATERSPOUT.]