Next to the pleasure which the earnest zoologist derives from study of the habits and structure of living animals, and his intelligent appreciation of their perfect adaptation to their modes of life, and the circumstances in which they are placed, is the interest he feels in eliminating fiction from truth, whilst comparing the fancies of the past with the facts of the present. As his knowledge increases, he learns that the descriptions by ancient writers of so-called "fabulous creatures" are rather distorted portraits than invented falsehoods, and that there is hardly one of the monsters of old which has not its prototype in Nature at the present day. The idea of the Lernean Hydra, whose heads grew again when cut off by Hercules, originated, as I have shown in another chapter, in a knowledge of the octopus; and in the form and movements of other animals with which we are now familiar we may, in like manner, recognise the similitude and archetype of the mermaid. But we must search deeply into the history of mankind to discover the real source of a belief that has prevailed in almost all ages, and in all parts of the world, in the existence of a race of beings uniting the form of man with that of the fish. A rude resemblance between these creatures of imagination and tradition and certain aquatic animals is not sufficient to account for that belief. It probably had its origin in ancient mythologies, and in the sculptures and pictures connected with them, which were designed to represent certain attributes of the deities of various nations. In the course of time the meaning of these was lost; and subsequent generations regarded as the portraits of existing beings effigies which were at first intended to be merely emblematic and symbolical. [Illustration: FIG. 1.--NOAH, HIS WIFE, AND THREE SONS, AS FISH-TAILED DEITIES. _From a Gem in the Florentine Gallery. After Calmet._] Early idolatry consisted, first, in separating the idea of the One Divinity into that of his various attributes, and of inventing symbols and making images of each separately; secondly, in the worship of the sun, moon, stars, and planets, as living existences; thirdly, in the deification of ancestors and early kings; and these three forms were often mingled together in strange and tangled confusion. Amongst the famous personages with whose history men were made acquainted by oral tradition was Noah. He was known as the second father of the human race, and the preserver and teacher of the arts and sciences as they existed before the Great Deluge, of which so many separate traditions exist among the various races of mankind. Consequently, he was an object of worship in many countries and under many names; and his wife and sons, as his assistants in the diffusion of knowledge, were sometimes associated with him.