The Lambertville record. [volume] (Lambertville, N.J.) 1872-1968, 1895-04-24
THE SPANS OF LIFE.
DIFFERENCES OF DURATION IN MEN
AND ANIMALS.

| One OF the Shortest Is that Of the May
Fly and Ono of the Longest the Ele-
phant's-Among Insects the Period of
Adult Life Varies Greatly.
An essay of Weismann, charming
and profound and written before the
obsession of logical theory had car
ried him into arid metaphysics, dis
oussed the duration of life in men and
animals. To many, perhaps to most,
living things, death comes unexpected
ly, with an ironical Indifference to the
period of the animals life or to its bus
mess of the moment. The man may be
preparing to be merry; the bird may be
a-building, the butterfly not yet dry
from the ohrysalis, when they are fallen
upon by blind misohance, by enemies
intent only on dinner or by unthinking
microbes. Confronted by such extrinsio
accidents, men cry out after their kind,
the poet attuning an Intellectual lam
entation, the moralist preaching, the
pagan urging to the day of pleasure,
but the naturalist must be dumb. His
opportunity comes with tho animals
that avoid or escape colliding fates, and
that yet after fixed period run down
like clock. The seeds of deaths appar-
emily have been lying inert in the body
and come to fatal maturity after lapse
of time that varies little among indi-
viduals of the same species, but that is
widely different among different kinds
of animals.
Threesoore and ten is the natural
period of mans life The elephant will
live 200 years, the horse but half CEN
fury Singing birds and fowls and pleas
ants will live for nearly 90 years, but
parrots, eagles, falcons and swans are
known to survive their century Some
live through nearly two centuries.
Queen ants and working ants may live
for years. Sir John Lubbock kept a
queen ant alive for 10 years, during all
which period she continued to lay fer
tile eggs, but the males live only few
days. Queen bees live two or three
years; workers and drones few months,
although indeed in one sense the death
of the latter is unnatural, as the work
ers drive them away from the stores Of
food, so that they perish of starvation.
Among insects generally the period Of
adult life varies greatly. Many, like
the May flies, dance in the sun only for
few hours; the sexes meet, the eggs
are deposited and the creatures die be-
fore nightfall. Many butterflies and
moths are unprovided with feeding Or
gans and live only few hours, others
for many days.
Leaving out of count certain minor
factors, like tho time required for grow
ing to larger size and the slower
growth of animals that must waste time
and energy in capturing living food, it
is certain that there is an intimate con-
nection all through the animal kingdom
petween the duration OF life and the
/ reproductive habits Animals, in one
sense, are like the bright and fragrant
flowers of plants; since when their
function is accomplished when seeds
are formed, they wither and perish.
The business of tho animal seems to be,
not to live its own life. but to reproduce
its own kind, and the term of life at its
disposal is adjusted accurately to the
special difficulties Of this purpose.
Weismann and Alfred Russell Wallace
suggest that death comes as soon as pos
sible after the due number of successors
has been produced, in order that each
species may always BIO represented by a
full tale of young and vigorous indivi-
duals. Natural selection acts like con-
tractor who has undertaken to keep
window box gay with fresh blossoms;
each plant must be removed almost be-
fore its flowers fade
But our present concern is with the
fact rather than with explanation Of the
fact. Taking the needs Of reproduction
as master key, we find 1t unlocking
the secrets of inequalities of life. The
May flies live only q few hours, but
their eggs are produced abundantly and
have only to be dropped into pools from
which their parents, leaving their chrys-
ais, sprang into the sunny air. The
short lived moths and butterflies SINH
larly are untroubled by family cares.
When the eggs have to be deposited on
common and abundant food plants the
females need and possess few hours in
which to accomplish their easy task.
The males, ON the other hand, have to
fly about seeking and sometimes fight
ing for possession of the females, and
to them longer life is allotted. But
terfiies and moths that live for moro
than few days are those whose cater
pillars require a rarer food plant, q
more carefully chosen nursery and feed
ing ground Tho females have to fly
about seeking convenient spots for their
offspring. and tho eggs, instead of ripen-
ing and being deposited simultaneous
ly, are laid from day to day until the
full tale DO accomplished. In many
tribes of bees the males play their part
but once, and that during the nuptial
flight of the queen. Immediately after
ward they die or shortly after are killed
by the workers. The queens, secluded in
the middle of the hive, produce crops
of workers year after year, and 30 their
lives are prolonged. t
Among the birds and beasts parental
cares have brought length Of days with
them. The small singing birds are rapid
breeders, sometimes producing five or
sex nestlinRs twice a year, but their
enemies are equally numerous, and de-
spite the constant attention of the ma!s
and female play such havoc with the
young that hardly in 20 years will
pair rear up young enough to maintain
the species. Birds like pheasants and
fowls are still more prolific, but old
and young like are preyed upon by null
titude of enemies. The birds of prey are
slow breeders. Their active fight makes
1t impossible that the females should
carry with them burden Of developing
eggs, and in their long lives they leave
behind them no more progeny than
quicker breoding, shorter lived crea-
lures Saturday Review.
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