All the animals of these numerous Classes have a back-bone; but if we examine a nautilus, a snail, a beetle, a worm, a coral, or an animalcule, nothing like an internal skeleton made up of bones, some of which are placed inside the back, can be discovered. Hence all the animals can be arranged into two SUB-KINGDOMS, those with and those without back-bones, or the Vertebrata and the Invertebrata. (The name _vertebrata_ is taken from the Latin word _vertebra_, which means a turning-joint in the body, or a back-bone.) Those are the sub-kingdoms of the animal KINGDOM, which is so called in contradistinction to the _kingdom_ of plants. It must be remembered, however, that the best classification is but an attempt of a finite understanding to arrange the infinitely variable things of Nature. It is but an artificial and arbitrary arrangement which is necessary for study: for were the whole truth before us, there would be no classification which would depend on marked differences in shape and internal construction. Were the figures and anatomy of every animal that has lived, and of every creature which is now living on the globe, placed before us, the gaps which enable one genus to be separated from another would be filled up, and even species would cease to be distinguished. But, in spite of the artificial nature of the classifications, there is this to be said of them: that they give some faint indications of the philosophy of creation. The differences and resemblances of animals relate to structures of the body which have been inherited from creatures that lived in the remote past; and we glean this when it is known that the young unborn of one genus resembles the old and fully-formed creatures of kinds belonging to other classes which preceded it in the history of the globe, and when it is shown by the microscope that some of the parts of the bodies of the most insignificant animals of the invertebrate sub-kingdom resemble those of the most gifted of animals. A classification thus opens out a little of the scheme of Nature, and it proves that the resemblances and differences of animals are not matters of chance, but that there is a law which has produced them. Such a law, yet perhaps not fully comprehended, is Man’s idea of the action of the will of the Divine Creator. [Illustration] CASSELL’S NATURAL HISTORY. [Illustration: GROUP OF APES AND MONKEYS, AND A LEMUR.] CLASS MAMMALIA. ORDER I.--QUADRUMANA.--THE APES AND MONKEYS. CHAPTER I. INTRODUCTION--THE MAN-SHAPED APES--1. THE GORILLA (_Troglodytes Gorilla_).