The sun., 1889-12-08

could escape all Jdtdt accldents tnTouRn IN
fnite time-a suppositlon which Is OF course
hardly conceivable. The individual would
nevertheless be unable TO avoid from time to
time slight injuries to one or another part
OF it's body. The injured parts could not regain
their former integrity, and thus the longer the
Individual lived the more defective and Grip
pied It would become. and the less perfectly
would it fulll the purpose OF it's species. In
diyiduals are injured by the operation OF ex-
ternal forces and for this reason alone 1t is nee
essary that new and perfect individuals should
continually arise and take their places, and
this necessity would remain even II the lndi-
vlduals possessed the power OF living eter-
nally." We may say in passing that we arc not
greatlyimpressed with the coRency OF this ar
gument In It's application to the higher animals
or, at all events, to man. In what sense Is
II true that crippled immortal would "imper-
fectly fulfil the purpose OF its species" DR..
Weismann himself contends that all acquired
characters. and a Jortiori mutilations, are non
transmissible. An immortal individual would
not therefore. because 1t was crippled, cease
TO bear or beget perfect offspring. On the
other hand. II we pass from the function OF re-
production to tho function Of tending, protect
Ing and instruotinR we must recognize that
the immortal individual might bo OF immense
benefit to the species through Its vast accumu-
lations OF experience and knowledge and the
superlative development OF Its insight and
sagaoity.
But to proceed with the outline OF Dr. Weis-
mann's views He attributes death not to
causes inherent in organs. but to influences
incident to the process OF natural selection
which aims at the advantage OF the species.
He considers. in other words. that death is not
primary necessity, but has been secondarily
acquired In tho effort at adaptation. He be-
Eeyes that life is endowed with a fixed dura-
tion, not because It is contrary to It's nature to
be unlimited, but because the unlimited exist
ence OF individuals would be luxury without
any corresponding benefit He believes. In
fine, that the organism did not cease to renew
the worn -out cell material because the nature
Of the cells did not permit them to multiply
indefinitely, but because the power OF multi
plying indefinitely was lost when 1t ceased to
be OF use. His ultimate conclusion being thus
formulated. Dr. Weismann goes on to show
how the adaptation which produced death was
effected,
1t is not true. although 1t is usually assumed,
that death 10 an attribute OF all organisms. An
immense number OF low organisms do not die.
although they are easily destroyed by external
agencies. In laying down this fundamental
proposition DR.. Weismann has in mind not only
the AmebB and the low unicellular AlgB.
but also far more highly organized unicellular
animals. such as the Infusoria. To be sure.
the life Of an individual Am9ba is generally
assumed to come to an end with the process
OF fission or division, which gives rise to two
new individuals. DR.. Weismann denies that
this process can truly be called death.
Where" asks. "is the dead body2 What
is It that dles2 Nothing dies: the body Of the
animal only divides into two similar parts.
possessing the same constitution. Each OF
these parts is exactly like its parent.
lives In the Same manner and finally divides
into two halves" Neither are there. he says.
any grounds for the assumption that the two
halves OF an AmPba are differently constituted
internally, SO that after q time one of them will
die while the other will continue to live. On
the contrary, such an assumption Is dlsDroved
by O recently discovered fact We have as little
reason for asserting that the AmGba. upon
flssion, disappears as an individual. If We
can" says DR.. Weismann. imagine an Ampba
endowed with self-consciousness 1t might
think before dividing: I will give birth to q
daughter and have no doubt that each half
would regard the other as a daughter and
would consider itself to be the original parent"
OF course we cannot appeal to the criterion
OF personality In the Am9ba. but we can ap-
peal to another criterion apparently decisive,
LQBL. uBuoly OI CONTINUITY Oh lOTu.
But why should unicellular animals be i'm
mortal2 Why shotfd not the touchstone of
utility condemn them also to death Because
they are too simply organized to undergo the
slight mutilation and deterioration due to the
accidents inseparable from an unlimited dura-
tion Of life. II an infusorian is injured by the
loss OF some part OF its body. 1t either repro
duces the part missing, or, II the injury be too
great. II dies. The alternative Is always per-
feet integrity or complete destruction. Normal
death. or death arising from internal causes. Is
therefore impossible among the lower unicel-
lular organisms. 1t remains to consider how
It happened that the multicelular animals
and plants which arose from unicellular forms
OF life came to lose the power OF living forever.
The answer to this question Is bound up with
the principle OF division Of labor which ap-
peared among multicellular organisms at
very early stage. and has gradually led to the
production Of greater and greater complexities
In their structure
AS We have now reached the core OF the
hypothesis. or demonstration. by which the
author would account for the appearance of
death, we reproduce in his own words pas
sage OF considerable length: " The first multi
cellular organism was probably a cluster of
similar cells, but these units soon lost their
original homoReneity. AS the result Of mere
relative position. some OF the cells were es-
peciallV fitted to provide ior the nutrition OF
the colony. while others undertook the work Of
reproduction. Hence the single group would
come to be divided into two groups Of cells.
which may be called somatic and reproductive
tho cells Of the body or soma dedicated to
the Individually as opposed to those which are
concerned with reproduction dedicated to the
species.) This differentiation was not at first
absolute. and. indeed. Is not always so to-day
Among the lower Metazoa, such as the rolyps
the capacity for reproduction still exists to
such o degree In the somatic cells that
small number Of them are able to give
rise to a new oraanism-in fact. new indi-
viduals are normally produced by means OF So
called buds Furthermore. 1t is well known
that many OF the higher animals have retained
powers OF regeneration; the sala-
can replace its lost tail or foot. and
the snail can reproduce its horns. eyes, &C.
AS the oomplexity Of the Metazoan body In
creased the two groups of cells became more
sharply separated from each otner. Very soon
the somatlo cells surpassed the reproductive