"All beings are exposed to more or less frequent dangers, and are constantly struggling to defend their lives. They have to dread the inclemency of the seasons, and must perish if they fail to find a sufficiency of food; the herbivorous are destined to become a prey to the carnivorous, and, when there seems no need of a victim, deadly battles occur for the possession of a place or the conquest of a prize. Destruction is a natural law; but this destruction is restrained within certain limits: notwithstanding the perils that incessantly threaten the existence of all creatures, everything works actively to secure the maintenance of races. That instinct of preservation which goads individuals to fly from danger and seek the satisfaction of their material wants, allows many to escape accidents. If the causes of violent death vary within the widest range among animal species, they are always proportioned to the causes that protect against it. Fecundity, restricted among powerful animals, and limited also in those that have only the attacks of the strongest to fear, is prodigious among the weakest that are doomed to yield a multitude of victims. Thus the complete disappearance of any species is only possible under wholly exceptional conditions.".