a critical examination of on the origin of species-第3章

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evidence　in　favour　of　the　descent　of　those　animals　from　a　common
original。

To　turn　to　another　kind　of　illustration：If　you　regard　the　whole　series
of　stratified　rocksthat　enormous　thickness　of　sixty　or　seventy
thousand　feet　that　I　have　mentioned　before；　constituting　the　only
record　we　have　of　a　most　prodigious　lapse　of　time；　that　time　being；　in
all　probability；　but　a　fraction　of　that　of　which　we　have　no　record；if
you　observe　in　these　successive　strata　of　rocks　successive　groups　of
animals　arising　and　dying　out；　a　constant　succession；　giving　you　the
same　kind　of　impression；　as　you　travel　from　one　group　of　strata　to
another；　as　you　would　have　in　travelling　from　one　country　to
another；when　you　find　this　constant　succession　of　forms；　their　traces
obliterated　except　to　the　man　of　science；when　you　look　at　this
wonderful　history；　and　ask　what　it　means；　it　is　only　a　paltering　with
words　if　you　are　offered　the　reply；'They　were　so　created。'

But　if；　on　the　other　hand；　you　look　on　all　forms　of　organized　beings　as
the　results　of　the　gradual　modification　of　a　primitive　type；　the　facts
receive　a　meaning；　and　you　see　that　these　older　conditions　are　the
necessary　predecessors　of　the　present。　　Viewed　in　this　light　the　facts
of　palaeontology　receive　a　meaningupon　any　other　hypothesis；　I　am
unable　to　see；　in　the　slightest　degree；　what　knowledge　or　signification
we　are　to　draw　out　of　them。　　Again；　note　as　bearing　upon　the　same
point；　the　singular　likeness　which　obtains　between　the　successive
Faunae　and　Florae；　whose　remains　are　preserved　on　the　rocks：　you　never
find　any　great　and　enormous　difference　between　the　immediately
successive　Faunae　and　Florae；　unless　you　have　reason　to　believe　there
has　also　been　a　great　lapse　of　time　or　a　great　change　of　conditions。
The　animals；　for　instance；　of　the　newest　tertiary　rocks；　in　any　part　of
the　world；　are　always；　and　without　exception；　found　to　be　closely
allied　with　those　which　now　live　in　that　part　of　the　world。　　For
example；　in　Europe；　Asia；　and　Africa；　the　large　mammals　are　at　present
rhinoceroses；　hippopotamuses；　elephants；　lions；　tigers；　oxen；　horses；
etc。；　and　if　you　examine　the　newest　tertiary　deposits；　which　contain
the　animals　and　plants　which　immediately　preceded　those　which　now　exist
in　the　same　country；　you　do　not　find　gigantic　specimens　of　ant…eaters
and　kangaroos；　but　you　find　rhinoceroses；　elephants；　lions；　tigers；
etc。；of　different　species　to　those　now　living；but　still　their　close
allies。　　If　you　turn　to　South　America；　where；　at　the　present　day；　we
have　great　sloths　and　armadilloes　and　creatures　of　that　kind；　what　do
you　find　in　the　newest　tertiaries？　　You　find　the　great　sloth…like
creature；　the　'Megatherium'；　and　the　great　armadillo；　the　'Glyptodon'；
and　so　on。　　And　if　you　go　to　Australia　you　find　the　same　law　holds
good；　namely；　that　that　condition　of　organic　nature　which　has　preceded
the　one　which　now　exists；　presents　differences　perhaps　of　species；　and
of　genera；　but　that　the　great　types　of　organic　structure　are　the　same
as　those　which　now　flourish。

What　meaning　has　this　fact　upon　any　other　hypothesis　or　supposition　than
one　of　successive　modification？　　But　if　the　population　of　the　world；　in
any　age；　is　the　result　of　the　gradual　modification　of　the　forms　which
peopled　it　in　the　preceding　age；if　that　has　been　the　case；　it　is
intelligible　enough；　because　we　may　expect　that　the　creature　that
results　from　the　modification　of　an　elephantine　mammal　shall　be
something　like　an　elephant；　and　the　creature　which　is　produced　by　the
modification　of　an　armadillo…like　mammal　shall　be　like　an　armadillo。
Upon　that　supposition；　I　say；　the　facts　are　intelligible；　upon　any
other；　that　I　am　aware　of；　they　are　not。

So　far；　the　facts　of　palaeontology　are　consistent　with　almost　any　form
of　the　doctrine　of　progressive　modification；　they　would　not　be
absolutely　inconsistent　with　the　wild　speculations　of　De　Maillet；　or
with　the　less　objectionable　hypothesis　of　Lamarck。　　But　Mr。　Darwin's
views　have　one　peculiar　merit；　and　that　is；　that　they　are　perfectly
consistent　with　an　array　of　facts　which　are　utterly　inconsistent　with
and　fatal　to；　any　other　hypothesis　of　progressive　modification　which
has　yet　been　advanced。　　It　is　one　remarkable　peculiarity　of　Mr。
Darwin's　hypothesis　that　it　involves　no　necessary　progression　or
incessant　modification；　and　that　it　is　perfectly　consistent　with　the
persistence　for　any　length　of　time　of　a　given　primitive　stock；
contemporaneously　with　its　modifications。　　To　return　to　the　case　of　the
domestic　breeds　of　pigeons；　for　example；　you　have　the　Dove…cot　pigeon；
which　closely　resembles　the　Rock　pigeon；　from　which　they　all　started；
existing　at　the　same　time　with　the　others。　　And　if　species　are
developed　in　the　same　way　in　nature；　a　primitive　stock　and　its
modifications　may；　occasionally；　all　find　the　conditions　fitted　for
their　existence；　and　though　they　come　into　competition；　to　a　certain
extent；　with　one　another；　the　derivative　species　may　not　necessarily
extirpate　the　primitive　one；　or　'vice　versa'。

Now　palaeontology　shows　us　many　facts　which　are　perfectly　harmonious
with　these　observed　effects　of　the　process　by　which　Mr。　Darwin　supposes
species　to　have　originated；　but　which　appear　to　me　to　be　totally
inconsistent　with　any　other　hypothesis　which　has　been　proposed。　There
are　some　groups　of　animals　and　plants；　in　the　fossil　world；　which　have
been　said　to　belong　to　〃persistent　types；〃　because　they　have　persisted；
with　very　little　change　indeed；　through　a　very　great　range　of　time；
while　everything　about　them　has　changed　largely。　　There　are　families　of
fishes　whose　type　of　construction　has　persisted　all　the　way　from　the
carboniferous　rock　right　up　to　the　cretaceous；　and　others　which　have
lasted　through　almost　the　whole　range　of　the　secondary　rocks；　and　from
the　lias　to　the　older　tertiaries。　　It　is　something　stupendous　thisto
consider　a　genus　lasting　without　essential　modifications　through　all
this　enormous　lapse　of　time　while　almost　everything　else　was　changed
and　modified。

Thus　I　have　no　doubt　that　Mr。　Darwin's　hypothesis　will　be　found
competent　to　explain　the　majority　of　the　phenomena　exhibited　by　species
in　nature；　but　in　an　earlier　lecture　I　spoke　cautiously　with　respect　to
its　power　of　explaining　all　the　physiological　peculiarities　of　species。

There　is；　in　fact；　one　set　of　these　peculiarities　which　the　theory　of
selective　modification；　as　it　stands　at　present；　is　not　wholly
competent　to　explain；　and　that　is　the　group　of　phenomena　which　I
mentioned　to　you　under　the　name　of　Hybridism；　and　which　I　explained　to
consist　in　the　sterility　of　the　offspring　of　certain　species　when
crossed　one　with　another。　　It　matters　not　one　whit　whether　this
sterility　is　universal；　or　whether　it　exists　only　in　a　single　case。
Every　hypothesis　is　bound　to　explain；　or；　at　any　rate；　not　be
inconsistent　with；　the　whole　of　the　facts　which　it　professes　to　account
for；　and　if　there　is　a　single　one　of　these　facts　which　can　be　shown　to
be　inconsistent　with　（I　do　not　merely　mean　inexplicable　by；　but　contrary
to）　the　hypothesis；　the　hypothesis　falls　to　the　ground；it　is　worth
nothing。　　One　fact　with　which　it　is　positively　inconsistent　is　worth　as
much；　and　as　powerful　in　negativing　the　hypothesis；　as　five　hundred。　If
I　am　right　in　thus　defining　the　obligations　of　an　hypothesis；　Mr。
Darwin；　in　order　to　place　his　views　beyond　the　reach　of　all　possible
assault；　ought　to　be　able　to　demonstrate　the　possibility　of　developing
from　a　particular　stock　by　selective　breeding；　two　forms；　which　should
either　be　unable　to　cross　one　with　another；　or　whose　cross…bred
offspring　should　be　infertile　with　one　another。

For；　you　see；　if　you　have　not　done　that　you　have　not　strictly　fulfilled
all　the　conditions　of　the　problem；　you　have　not　shown　that　you　can
produce；　by　the　cause　assumed；　all　the　phenomena　which　you　have　in
nature。　　Here　are　the　phenomena　of　Hybridism　staring　you　in　the　face；
and　you　cannot　say；　'I　can；　by　selective　modification；　produce　these
same　results。'　　Now；　it　is　admitted　on　all　hands　that；　at　present；　so
far　as　experiments　have　gone；　it　has　not　been　found　possible　to　produce
this　complete　physiolo