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Show TEE SPAiATS OS1 LIFE. DIFFERENCES OF DURAIrON IN MEN AND ANIMALS. One of tho Shortest Is that of the Ma Fly and One of the Longest the Elephant's Ele-phant's Among Insects the Period o Adult Life Varies Greatly. An essay of Weismann, charming and profound and written before the obsession of a logical theory had car ried him into arid metaphysics, dis-anssed dis-anssed the duration of life in men and animala To many, perhaps to most ' living things, death comes unexpectedly, unexpected-ly, with an ironical indifference to the period of the animal's life or to its business bus-iness of the moment. The man may bo preparing to be merry; the bird may bs -building, tho butterfly not yet dry from tho chrysalis, when they are fallen apon by blind mischance, by eDemie? intent only on dinnor or by unthinking microbes. Coufrouted by such extrinsic accidents, men cry out after their kind, tho poet attuning an ineffectual lamentation, lam-entation, the moralist preaching, tho pagan urging to tho day of ploasure, but tho naturalist must bo dumb. His opportunity comes with tbo animals that avoid or escape colliding fates, and that yet after a fixed period run down like a clock. The seeds of deaths apparently appar-ently have been lying inert in tho body and coma to fatal maturity after a lapse of time that varies little among individuals indi-viduals of tbo saino species, but that is widely different among different kinds of animals. Threescore and ten is tho natural oeriod of man'? life. The elephant will live 200 years, t'&e horo but half a century. cen-tury. Singing birds and fowls and pheasants pheas-ants will live for nearly 20 years, but parrots, eagles, falcons and swans are known to survive their century. Some livo Jhrough nearly two centuries. Queen ants and working ants may live for years. Sir John Lubbock kept a queen ant alivo for 13 years, during all which period she continued to lay fer-tilo fer-tilo eggs, but the males livo only a few days. Quenn bees livo two or throe years; workers and drones a fow months, although indeed in one sense the death of the latter ia unnatural, as the workers work-ers drive thorn away from the stores of food, so that they peribh of starvation. Among insects generally the period of adult life varios greatly. Many, like she May flies, dance in tho sun only for a few hours; tho sosos meet, the eggs are deposited and tho creatures die before be-fore nightfall. Many butterflies and moths are unprovided with feeding organs or-gans and livo only a few hours, others for many days. Leaving out of count certain minor factors, like the time required for growing grow-ing to a larger size and tho slower growth of animals that must waste time and energy in capturing living food, it is certain that thero is an intimate connection con-nection all through the animal kingdom between the duration of life and the reproductive habits. Animals, in one sense, aro like tho bright and fragrant flowers of plants; since when their function is accomplished, when seeds aro formed, they wither and perish. Tho business of the animal Eeems to bo, not to livo its own life, but to reproduce its own kind, and tho term of life at its disposal is adjusted accurately to the special difficulties of this purpose. Weismann and Alfred Russel Wallace suggest that death comes as soon as pos-tible pos-tible after tho due number of successors has been produced, In order that each species may always bo represented by a full tale of young and vigorous individuals. indivi-duals. Natural selection acts like aeon-tractor aeon-tractor who has undertaken to keep a window bos gay with fresh blossoms; eaoh plant must be removed almost before be-fore its flowers fade. But our present concern fs with the fact rather than with explanation 'of tho fact. Taking the needs of reproduction as a master key, we find it unlocking tho secrets of inequalities of life. Tho May flies live only a few hours, but their eggs are produced abundantly and have only to bo dropped into pools from which their parents, leaving their chrysalis, chrys-alis, sprang into the sunny air. The short lived moths and butterflies similarly simi-larly aro untroubled by family cares. When the eggs have to bo deposited on common and abundant food plants tho fsmales need and possess few hours in which to accomplish their easy task. Tho males, on the other hand, have to fly about seeking and sometimes fighting fight-ing for possession of tho females, and to them a longer life is t.llottod. Butterflies But-terflies and moths that live for more than a few days are thoso whoso caterpillars cater-pillars require a rarer food plant, a more carefully chosen nursery and feed ing ground. The fomilos have to fly about seeking convenient spots for their offspring, and tho eggs, instead of ripening ripen-ing and being deposited simultaneous ly, are laid from day to day until the full tale bo accomplished. In manj tribes of bees tho males play their par' but once, and that during the nuptia-' flight of the queou. Immediately afterward after-ward they die or shortly after aro killed by the workers. The queens, secluded in the middle of the hivo, produce crops of workers year after year, and so their lives are prolonged. Among the birds and beasts parental cares have brought length of days with them. Tho small singing birds aro rapia breeders, sometimes producing five or sex nestlings twice a year, but their enemies are equally numerous, and despite de-spite the constant attention of tho male and female play such havoc with the young that hardly in 20 years will a pair rear up young enough to maintain the species. Birds like pheasants and fowls are still more prolific, but old uid vouniz like are nrovod nnmi liv n mnl- ritude of enemies. The birds of prey are slow breeders. Their active flight makes it impossible that the females should carry with them a burden of developing eggs, and in their long lives they leave behind them no more progeny than quicker breeding, shorter lived croa-turoB croa-turoB Saturday Ry low, fciohoolboy (wearily) What's tho ns of learning nil this stuff? Teacher It is chiefly to cultivate the memory. Schoolboy Don't you think it would be more sensible to buy a phonograph? Good News. |