It is a fact that the increase in the birth of animals is greater than the existing food permits of sustaining. There is no exception to the rule that all organic beings tend to increase so rapidly that our earth would be overrun very soon by the offspring of a single pair, were these not destroyed. It is for this reason that a struggle for existence must arise. Every animal tries to live, does its best to eat, and seeks to avoid being eaten by others. With its particular peculiarities and weapons it struggles against the entire antagonistic world, against animals, cold, heat, dryness, inundations, and other natural occurrences that may threaten to destroy it. Above all, it struggles with the animals of its own kind, who live in the same way, have the same peculiarities, use the same weapons and live by the same nourishment. This struggle is not a direct one; the hare does not struggle directly with the hare, nor the lion with the lion――unless it is a struggle for the female――but it is a struggle for existence, a race, a competitive struggle. All of them can not reach a grown-up age; most of them are destroyed, and only those who win the race remain. But which are the ones to win in the race? Those which, through their peculiarities, through their bodily structures are best able to find food or to escape an enemy; in other words, those which are best adapted to existing conditions will survive. “Because there are ever more individuals born than can remain alive, the struggle as to which shall remain alive must start again and that creature that has some advantage over the others will survive, but as these diverging peculiarities are transmitted to the new generations, nature itself does the choosing, and a new generation will arise having changed peculiarities.” Here we have another application for the origin of the giraffe. When grass does not grow in some places, the animals must nourish themselves on tree leaves, and all those whose necks are too short to reach these leaves must perish. In nature itself there is selection, and nature selects only those having long necks. In conformity with the selection done by the animal breeder, Darwin called this process “natural selection.” This process must necessarily produce new species. Because too many are born of a certain species, more than the existing food supply can sustain, they are forever trying to spread over a larger area. In order to procure their food, those living in the woods go to the plain, those living on the soil go into the water, and those living on the ground climb on trees. Under these new conditions divergence is necessary. These divergencies are increased, and from the old species a new one develops. This continuous movement of existing species branching out into new relations results in these thousands of different animals changing still more.