essays on life, art and science-第40章

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sufficiently　observed。　　The　recent　experiments　themselves　are　only
described　in　short　preliminary　notices；　which；　as　regards　their
accuracy；　the　possibility　of　mistake；　the　precautions　taken；　and　the
exact　succession　of　individuals　affected；　afford　no　data　on　which　a
scientific　opinion　can　be　founded〃　（pp。　81；　82）。

The　line　Professor　Weismann　takes；　therefore；　is　to　discredit　the
facts；　yet　on　a　later　page　we　find　that　the　experiments　have　since
been　repeated　by　Obersteiner；　〃who　has　described　them　in　a　very
exact　and　unprejudiced　manner；〃　and　that　〃the　fact〃（I　imagine　that
Professor　Weismann　intends　〃the　facts〃）〃cannot　be　doubted。〃

On　a　still　later　page；　however；　we　read：…

〃If；　for　instance；　it　could　be　shown　that　artificial　mutilation
spontaneously　reappears　in　the　offspring　with　sufficient　frequency
to　exclude　all　possibilities　of　chance；　then　such　proof　＇i。e。；　that
acquired　characters　can　be　transmitted＇　would　be　forthcoming。　　The
transmission　of　mutilations　has　been　frequently　asserted；　and　has
been　even　recently　again　brought　forward；　but　all　the　supposed
instances　have　broken　down　when　carefully　examined〃　（p。　390）。

Here；　then；　we　are　told　that　proof　of　the　occasional　transmission　of
mutilations　would　be　sufficient　to　establish　the　fact；　but　on　p。　267
we　find　that　no　single　fact　is　known　which　really　proves　that
acquired　characters　can　be　transmitted；　〃FOR　THE　ASCERTAINED　FACTS
WHICH　SEEM　TO　POINT　TO　THE　TRANSMISSION　OF　ARTIFICIALLY　PRODUCED
DISEASES　CANNOT　BE　CONSIDERED　AS　PROOF〃　＇Italics　mine。＇　　Perhaps；
but　it　was　mutilation　in　many　cases　that　Professor　Weismann
practically　admitted　to　have　been　transmitted　when　he　declared　that
Obersteiner　had　verified　Brown…Sequard's　experiments。

That　Professor　Weismann　recognises　the　vital　importance　to　his　own
theory　of　the　question　whether　or　no　mutilations　can　be　transmitted
under　any　circumstances；　is　evident　from　a　passage　on　p。　425　of　his
work；　on　which　he　says：　　〃It　can　hardly　be　doubted　that　mutilations
are　acquired　characters；　they　do　not　arise　from　any　tendency
contained　in　the　germ；　but　are　merely　the　reaction　of　the　body　under
certain　external　influences。　　They　are；　as　I　have　recently　expressed
it；　purely　somatogenic　charactersviz。；　characters　which　emanate
from　the　body　（soma）　only；　as　opposed　to　the　germ…cells；　they　are；
therefore；　characters　that　do　not　arise　from　the　germ　itself。

〃If　mutilations　must　necessarily　be　transmitted〃　＇which　no　one　that
I　know　of　has　maintained＇；　〃or　even　if　they　might　occasionally　be
transmitted〃　＇which　cannot；　I　imagine；　be　reasonably　questioned＇；　〃a
powerful　support　would　be　given　to　the　Lamarckian　principle；　and　the
transmission　of　functional　hypertrophy　or　atrophy　would　thus　become
highly　probable。〃

I　have　not　found　any　further　attempt　in　Professor　Weismann's　book　to
deal　with　the　evidence　adduced　by　Mr。　Darwin　to　show　that
mutilations；　if　followed　by　diseases；　are　sometimes　inherited；　and　I
must　leave　it　to　the　reader　to　determine　how　far　Professor　Weismann
has　shown　reason　for　rejecting　Mr。　Darwin's　conclusion。　　I　do　not；
however；　dwell　upon　these　facts　now　as　evidence　of　a　transmitted
change　of　bodily　form；　or　of　instinct　due　to　use　and　disuse　or
habit；　what　they　prove　is　that　the　germ…cells　within　the　parent's
body　do　not　stand　apart　from　the　other　cells　of　the　body　so
completely　as　Professor　Weismann　would　have　us　believe；　but　that；　as
Professor　Hering；　of　Prague；　has　aptly　said；　they　echo　with　more　or
less　frequency　and　force　to　the　profounder　impressions　made　upon
other　cells。

I　may　say　that　Professor　Weismann　does　not　more　cavalierly　wave
aside　the　mass　of　evidence　collected　by　Mr。　Darwin　and　a　host　of
other　writers；　to　the　effect　that　mutilations　are　sometimes
inherited；　than　does　Mr。　Wallace；　who　says　that；　〃as　regards
mutilations；　it　is　generally　admitted　that　they　are　not　inherited；
and　there　is　ample　evidence　on　this　point。〃　　It　is　indeed　generally
admitted　that　mutilations；　when　not　followed　by　disease；　are　very
rarely；　if　ever；　inherited；　and　Mr。　Wallace's　appeal　to　the　〃ample
evidence〃　which　he　alleges　to　exist　on　this　head；　is　much　as　though
he　should　say　that　there　is　ample　evidence　to　show　that　the　days　are
longer　in　summer　than　in　winter。　　〃Nevertheless；〃　he　continues；　〃a
few　cases　of　apparent　inheritance　of　mutilations　have　been　recorded；
and　these；　if　trustworthy；　are　difficulties　in　the　way　of　the
theory。〃　。　。　。　〃The　often…quoted　case　of　a　disease　induced　by
mutilation　being　inherited　（Brown…Sequard's　epileptic　guinea…pigs）
has　been　discussed　by　Professor　Weismann　and　shown　to　be　not
conclusive。　　The　mutilation　itselfa　section　of　certain　nerveswas
never　inherited；　but　the　resulting　epilepsy；　or　a　general　state　of
weakness；　deformity；　or　sores；　was　sometimes　inherited。　　It　is；
however；　possible　that　the　mere　injury　introduced　and　encouraged　the
growth　of　certain　microbes；　which；　spreading　through　the　organism；
sometimes　reached　the　germ…cells；　and　thus　transmitted　a　diseased
condition　to　the　offspring。〃　｛35｝

I　suppose　a　microbe　which　made　guinea…pigs　eat　their　toes　off　was
communicated　to　the　germ…cells　of　an　unfortunate　guinea…pig　which
had　been　already　microbed　by　it；　and　made　the　offspring　bite　its
toes　off　too。　　The　microbe　has　a　good　deal　to　answer　for。

On　the　case　of　the　deterioration　of　horses　in　the　Falkland　Islands
after　a　few　generations；　Professor　Weismann　says：…

〃In　such　a　case　we　have　only　to　assume　that　the　climate　which　is
unfavourable；　and　the　nutriment　which　is　insufficient　for　horses；
affect　not　only　the　animal　as　a　whole　but　also　its　germ…cells。　　This
would　result　in　the　diminution　in　size　of　the　germ…cells；　the
effects　upon　the　offspring　being　still　further　intensified　by　the
insufficient　nourishment　supplied　during　growth。　　But　such　results
would　not　depend　upon　the　transmission　by　the　germ…cells　of　certain
peculiarities　due　to　the　unfavourable　climate；　which　only　appear　in
the　full…grown　horse。〃

But　Professor　Weismann　does　not　like　such　cases；　and　admits　that　he
cannot　explain　the　facts　in　connection　with　the　climatic　varieties
of　certain　butterflies；　except　〃by　supposing　the　passive　acquisition
of　characters　produced　by　the　direct　influence　of　climate。〃

Nevertheless　in　his　next　paragraph　but　one　he　calls　such　cases
〃doubtful；〃　and　proposes　that　for　the　moment　they　should　be　left
aside。　　He　accordingly　leaves　them；　but　I　have　not　yet　found　what
other　moment　he　considered　auspicious　for　returning　to　them。　　He
tells　us　that　〃new　experiments　will　be　necessary；　and　that　he　has
himself　already　begun　to　undertake　them。〃　　Perhaps　he　will　give　us
the　results　of　these　experiments　in　some　future　bookfor　that　they
will　prove　satisfactory　to　him　can　hardly；　I　think；　be　doubted。　　He
writes：…

〃Leaving　on　one　side；　for　the　moment；　these　doubtful　and
insufficiently　investigated　cases；　we　may　still　maintain　that　the
assumption　that　changes　induced　by　external　conditions　in　the
organism　as　a　whole　are　communicated　to　the　germ…cells　after　the
manner　indicated　in　Darwin's　hypothesis　of　pangenesis；　is　wholly
unnecessary　for　the　explanation　of　these　phenomena。　　Still　we　cannot
exclude　the　possibility　of　such　a　transmission　occasionally
occurring；　for　even　if　the　greater　part　of　the　effects　must　be
attributable　to　natural　selection；　there　might　be　a　smaller　part　in
certain　cases　which　depends　on　this　exceptional　factor。〃

I　repeatedly　tried　to　understand　Mr。　Darwin's　theory　of　pangenesis；
and　so　often　failed　that　I　long　since　gave　the　matter　up　in　despair。
I　did　so　with　the　less　unwillingness　because　I　saw　that　no　one　else
appeared　to　understand　the　theory；　and　that　even　Mr。　Darwin's
warmest　adherents　regarded　it　with　disfavour。　　If　Mr。　Darwin　means
that　every　cell　of　the　body　throws　off　minute　particles　that　find
their　way　to　the　germ…cells；　and　hence　into　the　new　embryo；　this　is
indeed　difficult　of　comprehension　and　belief。　　If　he　means　that　the
rhythms　or　vibrations　that　go　on　ceaselessly　in　every　cell　of　the
body　communicate　themselves　with　greater　or　less　accuracy　or
perturbation；　as　the　case　may　be；　to　the　cells　that　go　to　form
offspring；　and　that　since　the　char