The facts that I have cited show that death is not necessarily inherent in living organisms. Naegeli,[322] a well-known German botanist, has asserted even that natural death does not exist in nature. He points out that trees, more than a thousand years old, perish not by natural death, that is to say, by the gradual decay of their vitality, but by some catastrophe. [Illustration: FIG. 17.—_Chætogaster_ about to divide into four (from a drawing by M. Mesnil). ] The age of the famous dragontree of the Villa Oratava at Teneriffe, admired by Von Humboldt, was estimated at several thousand years. Its trunk was hollow, but the huge monster continued to flourish until it was overthrown by a storm. It was only by a catastrophe that the long-lived giant perished. The Baobab is reputed to live for five or six thousand years. In a recently published essay, Jacques Loeb,[323] a distinguished biologist in Chicago, has made a study of natural death, and has come to the conclusion that there is no good evidence for its existence. He has observed that ripe, but unfertilised eggs of sea hedgehogs (Echini) die a few hours after they have been discharged. Loeb thinks that this may be a case of natural death, but I cannot agree with this opinion, as an egg that has not been fertilised by a spermatozoon may be compared with an organism deprived of its nutrition and so dying of starvation. In both cases death is purely accidental and could have been avoided. If natural death does exist, it must have appeared on the face of the earth long after the appearance of life. Weismann has suggested that death arose as an adaptation for the advantage of the species, that is to say, in relation to the surrounding conditions of existence, and not as an absolute necessity inherent in the nature of the living substance. He thought that as worn organisms are no longer suited for reproduction or for the struggle for life, natural death was due to natural selection, it being necessary to maintain the species in a vigorous state by weeding out the debased individuals. But the introduction of death for that purpose was superfluous, since the debility caused by old age in itself would eliminate the aged in the course of the struggle for existence. Violent death must have appeared almost as soon as living things came into being. The infusorians and other low organisms, despite their potential immortality, must have been subjected perpetually to violent death, falling victims to larger and stronger organisms. It is impossible to regard natural death, if indeed it actually exists, as the product of natural selection for the benefit of the species. In the press of the world natural death rarely could come into operation, because maladies or the voracity of enemies so frequently cause violent death.