essays on life, art and science-第42章

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Darwin　so　much　in　the　background。　　Unwillingness　to　make　this
understood　is　nowhere　manifested　more　clearly　than　in　Dr。　Francis
Darwin's　life　of　his　father。　　In　this　work　Lamarck　is　sneered　at
once　or　twice；　and　told　to　go　away；　but　there　is　no　attempt　to　state
the　two　cases　side　by　side；　from　which；　as　from　not　a　little　else；　I
conclude　that　Dr。　Francis　Darwin　has　descended　from　his　father　with
singularly　little　modification。

Proceeding　to　the　evidence　for　the　transmissions　of　acquired　habits；
I　will　quote　two　recently　adduced　examples　from　among　the　many　that
have　been　credibly　attested。　　The　first　was　contributed　to　Nature
（March　14；　1889）　by　Professor　Marcus　M。　Hartog；　who　wrote：…

〃A。　B。　is　moderately　myopic　and　very　astigmatic　in　the　left　eye；
extremely　myopic　in　the　right。　　As　the　left　eye　gave　such　bad　images
for　near　objects；　he　was　compelled　in　childhood　to　mask　it；　and
acquired　the　habit　of　leaning　his　head　on　his　left　arm　for　writing；
so　as　to　blind　that　eye；　or　of　resting　the　left　temple　and　eye　on
the　hand；　with　the　elbow　on　the　table。　　At　the　age　of　fifteen　the
eyes　were　equalised　by　the　use　of　suitable　spectacles；　and　he　soon
lost　the　habit　completely　and　permanently。　　He　is　now　the　father　of
two　children；　a　boy　and　a　girl；　whose　vision　（tested　repeatedly　and
fully）　is　emmetropic　in　both　eyes；　so　that　they　have　not　inherited
the　congenital　optical　defect　of　their　father。　　All　the　same；　they
have　both　of　them　inherited　his　early　acquired　habit；　and　need
constant　watchfulness　to　prevent　their　hiding　the　left　eye　when
writing；　by　resting　the　head　on　the　left　forearm　or　hand。　　Imitation
is　here　quite　out　of　the　question。

〃Considering　that　every　habit　involves　changes　in　the　proportional
development　of　the　muscular　and　osseous　systems；　and　hence　probably
of　the　nervous　system　also；　the　importance　of　inherited　habits；
natural　or　acquired；　cannot　be　overlooked　in　the　general　theory　of
inheritance。　　I　am　fully　aware　that　I　shall　be　accused　of　flat
Lamarckism；　but　a　nickname　is　not　an　argument。〃

To　this　Professor　Ray　Lankester　rejoined　（Nature；　March　21；　1889）：…

〃It　is　not　unusual　for　children　to　rest　the　head　on　the　left　forearm
or　hand　when　writing；　and　I　doubt　whether　much　value　can　be　attached
to　the　case　described　by　Professor　Hartog。　　The　kind　of　observation
which　his　letter　suggests　is；　however；　likely　to　lead　to　results
either　for　or　against　the　transmission　of　acquired　characters。　　An
old　friend　of　mine　lost　his　right　arm　when　a　schoolboy；　and　has　ever
since　written　with　his　left。　　He　has　a　large　family　and
grandchildren；　but　I　have　not　heard　of　any　of　them　showing　a
disposition　to　left…handedness。〃

From　Nature　（March　21；　1889）　I　take　the　second　instance　communicated
by　Mr。　J。　Jenner…Weir；　who　wrote　as　follows：…

〃Mr。　Marcus　M。　Hartog's　letter　of　March　6th；　inserted　in　last　week's
number　（p。　462）；　is　a　very　valuable　contribution　to　the　growing
evidence　that　acquired　characters　may　be　inherited。　　I　have　long
held　the　view　that　such　is　often　the　case；　and　I　have　myself
observed　several　instances　of　the；　at　least　I　may　say；　apparent
fact。

〃Many　years　ago　there　was　a　very　fine　male　of　the　Capra　megaceros　in
the　gardens　of　the　Zoological　Society。　　To　restrain　this　animal　from
jumping　over　the　fence　of　the　enclosure　in　which　he　was　confined；　a
long；　and　heavy　chain　was　attached　to　the　collar　round　his　neck。　　He
was　constantly　in　the　habit　of　taking　this　chain　up　by　his　horns　and
moving　it　from　one　side　to　another　over　his　back；　in　doing　this　he
threw　his　head　very　much　back；　his　horns　being　placed　in　a　line　with
the　back。　　The　habit　had　become　quite　chronic　with　him；　and　was　very
tiresome　to　look　at。　　I　was　very　much　astonished　to　observe　that　his
offspring　inherited　the　habit；　and　although　it　was　not　necessary　to
attach　a　chain　to　their　necks；　I　have　often　seen　a　young　male
throwing　his　horns　over　his　back　and　shifting　from　side　to　side　an
imaginary　chain。　　The　action　was　exactly　the　same　as　that　of　his
ancestor。　　The　case　of　the　kid　of　this　goat　appears　to　me　to　be
parallel　to　that　of　child　and　parent　given　by　Mr。　Hartog。　　I　think
at　the　time　I　made　this　observation　I　informed　Mr。　Darwin　of　the
fact　by　letter；　and　he　did　not　accuse　me　of　'flat　Lamarckism。'〃

To　this　letter　there　was　no　rejoinder。　　It　may　be　said；　of　course；
that　the　action　of　the　offspring　in　each　of　these　cases　was　due　to
accidental　coincidence　only。　　Anything　can　be　said；　but　the　question
turns　not　on　what　an　advocate　can　say；　but　on　what　a　reasonably
intelligent　and　disinterested　jury　will　believe；　granted　they　might
be　mistaken　in　accepting　the　foregoing　stories；　but　the　world　of
science；　like　that　of　commerce；　is　based　on　the　faith　or　confidence；
which　both　creates　and　sustains　them。　　Indeed　the　universe　itself　is
but　the　creature　of　faith；　for　assuredly　we　know　of　no　other
foundation。　　There　is　nothing　so　generally　and　reasonably　accepted
not　even　our　own　continued　identitybut　questions　may　be　raised
about　it　that　will　shortly　prove　unanswerable。　　We　cannot　so　test
every　sixpence　given　us　in　change　as　to　be　sure　that　we　never　take　a
bad　one；　and　had　better　sometimes　be　cheated　than　reduce　caution　to
an　absurdity。　　Moreover；　we　have　seen　from　the　evidence　given　in　my
preceding　article　that　the　germ…cells　issuing　from　a　parent's　body
can；　and　do；　respond　to　profound　impressions　made　on　the　somatic…
cells。　　This　being　so；　what　impressions　are　more　profound；　what
needs　engage　more　assiduous　attention　than　those　connected　with
self…protection；　the　procuring　of　food；　and　the　continuation　of　the
species？　　If　the　mere　anxiety　connected　with　an　ill…healing　wound
inflicted　on　but　one　generation　is　sometimes　found　to　have　so
impressed　the　germ…cells　that　they　hand　down　its　scars　to　offspring；
how　much　more　shall　not　anxieties　that　have　directed　action　of　all
kinds　from　birth　till　death；　not　in　one　generation　only　but　in　a
longer　series　of　generations　than　the　mind　can　realise　to　itself；
modify；　and　indeed　control；　the　organisation　of　every　species？

I　see　Professor　S。　H。　Vines；　in　the　article　on　Weismann's　theory
referred　to　in　my　preceding　article；　says　Mr。　Darwin　〃held　that　it
was　not　the　sudden　variations　due　to　altered　external　conditions
which　become　permanent；　but　those　slowly　produced　by　what　he　termed
'the　accumulative　action　of　changed　conditions　of　life。'〃　　Nothing
can　be　more　soundly　Lamarckian；　and　nothing　should　more　conclusively
show　that；　whatever　else　Mr。　Darwin　was；　he　was　not　a　Charles…
Darwinian；　but　what　evidence　other　than　inferential　can　from　the
nature　of　the　case　be　adduced　in　support　of　this；　as　I　believe；
perfectly　correct　judgment？　　None　know　better　than　they　who　clamour
for　direct　evidence　that　their　master　was　right　in　taking　the
position　assigned　to　him　by　Professor　Vines；　that　they　cannot
reasonably　look　for　it。　　With　us；　as　with　themselves；　modification
proceeds　very　gradually；　and　it　violates　our　principles　as　much　as
their　own　to　expect　visible　permanent　progress；　in　any　single
generation；　or　indeed　in　any　number　of　generations　of　wild　species
which　we　have　yet　had　time　to　observe。　　Occasionally　we　can　find
such　cases；　as　in　that　of　Branchipus　stagnalis；　quoted　by　Mr。
Wallace；　or　in　that　of　the　New　Zealand　Kea　whose　skin；　I　was　assured
by　the　late　Sir　Julius　von　Haast；　has　already　been　modified　as　a
consequence　of　its　change　of　food。　　Here　we　can　show　that　in　even　a
few　generations　structure　is　modified　under　changed　conditions　of
existence；　but　as　we　believe　these　cases　to　occur　comparatively
rarely；　so　it　is　still　more　rarely　that　they　occur　when　and　where　we
can　watch　them。　　Nature　is　eminently　conservative；　and　fixity　of
type；　even　under　considerable　change　of　conditions；　is　surely　more
important　for　the　well…being　of　any　species　than　an　over…ready　power
of　adaptation　to；　it　may　be；　passing　changes。　　There　could　be　no
steady　progress　if　each　generation　were　not　mainly　bound　by　the
traditions　of　those　that　have　gone　before　it。　　It　is　evolution　and
not　incessant　revolution　that　both　parties　are　upholding；　and　this
being　so；　rapid　visible　modification　must　be　the　exception；　not　the
rule。