autobiography and selected essays-第29节

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the　Royal　Society　of　London；　which　never　had；　and　it　is　to　be　hoped

never　will　have；　anything　of　an　academic　constitution；　and　finally

he　took　himself　off　to　Guadaloupe；　and　became　lost　to　science

altogether。



Fifteen　or　sixteen　years　after　the　date　of　Peyssonel's　suppressed

paper；　the　Abbe　Trembley　＇118＇　published　his　wonderful　researches　upon

the　fresh…water　Hydra。　　Bernard　de　Jussieu　＇119＇　and　Guettard　＇120＇

followed　them　up　by　like　inquiries　upon　the　marine　sea…anemones　and

corallines；　Reaumur；　convinced　against　his　will　of　the　entire　justice

of　Peyssonel's　views；　adopted　them；　and　made　him　a　half…and…half

apology　in　the　preface　to　the　next　published　volume　of　the

〃Memoires　pour　servir　l'Histoire　des　Insectes；〃　and；　from　this　time

forth；　Peyssonel's　doctrine　that　corals　are　the　work　of　animal

organisms　has　been　part　of　the　body　of　established　scientific

truth。



Peyssonel；　in　the　extract　from　his　memoir　already　cited；　compares

the　flower…like　animal　of　the　coral　to　a　〃poulpe；〃　which　is　the

French　form　of　the　name　〃polypus；〃〃the　many…footed；〃which　the

ancient　naturalists　gave　to　the　soft…bodied　cuttlefishes；　which；

like　the　coral　animal；　have　eight　arms；　or　tentacles；　disposed

around　a　central　mouth。　　Reaumur；　admitting　the　analogy　indicated

by　Peyssonel；　gave　the　name　of　polypes；　not　only　to　the　sea…

anemone；　the　coral　animal；　and　the　fresh…water　Hydra；　but　to　what

are　now　known　as　the　Polyzoa；　and　he　termed　the　skeleton　which　they

fabricate　a　〃polypier；〃　or　〃polypidom。〃



The　progress　of　discovery；　since　Reaumur's　time；　has　made　us　very

completely　acquainted　with　the　structure　and　habits　of　all　these

polypes。　　We　know　that；　among　the　sea…anemones　and　coral…forming

animals；　each　poylpe　has　a　mouth　leading　to　a　stomach；　which　is

open　at　its　inner　end；　and　thus　communicates　freely　with　the

general　cavity　of　the　body；　that　the　tentacles　placed　round　the

mouth　are　hollow；　and　that　they　perform　the　part　of　arms　in　seizing

and　capturing　prey。　　It　is　known　that　many　of　these　creatures　are

capable　of　being　multiplied　by　artificial　division；　the　divided

halves　growing；　after　a　time；　into　complete　and　separate　animals；

and　that　many　are　able　to　perform　a　very　similar　process　naturally；

in　such　a　manner　that　one　polype　may；　by　repeated　incomplete

divisions；　give　rise　to　a　sort　of　sheet；　or　turf；　formed　by

innumerable　connected；　and　yet　independent；　descendants。　　Or；　what

is　still　more　common；　a　polype　may　throw　out　buds；　which　are

converted　into　polypes；　or　branches　bearing　polypes；　until　a　tree…

like　mass；　sometimes　of　very　considerable　size；　is　formed。



This　is　what　happens　in　the　case　of　the　red　coral　of　commerce。　　A

minute　polype；　fixed　to　the　rocky　bottom　of　the　deep　sea；　grows　up

into　a　branched　trunk。　　The　end　of　every　branch　and　twig　is

terminated　by　a　polype；　and　all　the　polypes　are　connected　together

by　a　fleshy　substance；　traversed　by　innumerable　canals　which　place

each　polype　in　communication　with　every　other；　and　carry

nourishment　to　the　substance　of　the　supporting　stem。　　It　is　a　sort

of　natural　cooperative　store；　every　polype　helping　the　whole；　at

the　same　time　as　it　helps　itself。　　The　interior　of　the　stem；　like

that　of　the　branches；　is　solidified　by　the　deposition　of　carbonate

of　lime　in　its　tissue；　somewhat　in　the　same　fashion　as　our　own

bones　are　formed　of　animal　matter　impregnated　with　lime　salts；　and

it　is　this　dense　skeleton　（usually　turned　red　by　a　peculiar

colouring　matter）　cleared　of　the　soft　animal　investment；　as　the

hard　wood　of　a　tree　might　be　stripped　of　its　bark；　which　is　the　red

coral。



In　the　case　of　the　red　coral；　the　hard　skeleton　belongs　to　the

interior　of　the　stem　and　branches　only；　but　in　the　commoner　white

corals；　each　polype　has　a　complete　skeleton　of　its　own。　　These

polypes　are　sometimes　solitary；　in　which　case　the　whole　skeleton　is

represented　by　a　single　cup；　with　partitions　radiating　from　its

centre　to　its　circumference。　　When　the　polypes　formed　by　budding　or

division　remain　associated；　the　polypidom　is　sometimes　made　up　of

nothing　but　an　aggregation　of　these　cups；　while　at　other　times　the

cups　are　at　once　separated　and　held　together；　by　an　intermediate

substance；　which　represents　the　branches　of　the　red　coral。　　The　red

coral　polype　again　is　a　comparatively　rare　animal；　inhabiting　a

limited　area；　the　skeleton　of　which　has　but　a　very　insignificant

mass；　while　the　white　corals　are　very　common；　occur　in　almost　all

seas；　and　form　skeletons　which　are　sometimes　extremely　massive。



With　a　very　few　exceptions；　both　the　red　and　the　white　coral

polypes　are；　in　their　adult　state；　firmly　adherent　to　the　sea…

bottom；　nor　do　their　buds　naturally　become　detached　and　locomotive。

But；　in　addition　to　budding　and　division；　these　creatures　possess

the　more　ordinary　methods　of　multiplication；　and；　at　particular

seasons；　they　give　rise　to　numerous　eggs　of　minute　size。　　Within

these　eggs　the　young　are　formed；　and　they　leave　the　egg　in　a

condition　which　has　no　sort　of　resemblance　to　the　perfect　animal。

It　is；　in　fact；　a　minute　oval　body；　many　hundred　times　smaller　than

the　full　grown　creature；　and　it　swims　about　with　great　activity　by

the　help　of　multitudes　of　little　hair…like　filaments；　called　cilia；

with　which　its　body　is　covered。　　These　cilia　all　lash　the　water　in

one　direction；　and　so　drive　the　little　body　along　as　if　it　were

propelled　by　thousands　of　extremely　minute　paddles。　　After　enjoying

its　freedom　for　a　longer　or　shorter　time；　and　being　carried　either

by　the　force　of　its　own　cilia；　or　by　currents　which　bear　it　along；

the　embryo　coral　settles　down　to　the　bottom；　loses　its　cilia；　and

becomes　fixed　to　the　rock；　gradually　assuming　the　polype　form　and

growing　up　to　the　size　of　its　parent。　　As　the　infant　polypes　of　the

coral　may　retain　this　free　and　active　condition　for　many　hours；　or

even　days；　and　as　a　tidal　or　other　current　in　the　sea　may　easily

flow　at　the　speed　of　two　or　even　more　miles　in　an　hour；　it　is　clear

that　the　embryo　must　often　be　transported　to　very　considerable

distances　from　the　parent。　　And　it　is　easily　understood　how　a

single　polype；　which　may　give　rise　to　hundreds；　or　perhaps

thousands；　of　embryos；　may；　by　this　process　of　partly　active　and

partly　passive　migration；　cover　an　immense　surface　with　its

offspring。



The　masses　of　coral　which　may　be　formed　by　the　assemblages　of

polypes　which　spring　by　budding；　or　by　dividing；　from　a　single

polype；　occasionally　attain　very　considerable　dimensions。　　Such

skeletons　are　sometimes　great　plates；　many　feet　long　and　several

feet　in　thickness；　or　they　may　form　huge　half　globes；　like　the

brainstone　corals；　or　may　reach　the　magnitude　of　stout　shrubs　or

even　small　trees。　　There　is　reason　to　believe　that　such　masses　as

these　take　a　long　time　to　form；　and　hence　that　the　age　a　polype

tree；　or　polype　turf；　may　attain；　may　be　considerable。　　But；　sooner

or　later；　the　coral　polypes；　like　all　other　things；　die；　the　soft

flesh　decays；　while　the　skeleton　is　left　as　a　stony　mass　at　the

bottom　of　the　sea；　where　it　retains　its　integrity　for　a　longer　or　a

shorter　time；　according　as　its　position　affords　more　or　less

protection　from　the　wear　and　tear　of　the　waves。



The　polypes　which　give　rise　to　the　white　coral　are　found；　as　has

been　said；　in　the　seas　of　all　parts　of　the　world；　but　in　the

temperate　and　cold　oceans　they　are　scattered　and　comparatively

small　in　size；　so　that　the　skeletons　of　those　which　die　do　not

accumulate　in　any　considerable　quantity。　　But　it　is　otherwise　in

the　greater　part　of　the　ocean　which　lies　in　the　warmer　parts　of　the

world；　comprised　within　a　distance　of　about　eighteen　hundred　miles

on　each　side　of　the　equator。　　Within　the　zone　thus　bounded；　by　far

the　greater　part　of　the　ocean　is　inhabited　by　coral　polypes；　which

not　only　form　very　strong　and　large　skeletons；　but　associate

together　into　great　masses；　like　the　thickets　and　the　meadow　turf；

or；　better　still；　the　accumulations　of　peat；　to　which　plants　give

rise　on　dry　land。　　These　masses　of　stony　matter；　heaped　up　beneath

the　waters　of　the　ocean；　become　as　dangerous　to　mariners　as　so　much

ordinary　rock；　and　to　these；　as　to　the　common　rock　ridges；　the

seaman　gives　the　name　of　〃reefs。〃



Such　coral　reefs　cover　many　thousand　square　miles　in　the　Pacific

and　in　the　Indian　Oceans。　　There　is　one　reef；　or　rather　great

series　of　reefs；　called　the　Barrier　Reef；　which　stretches；　almost

continuously；　for　more　than　eleven　hundred　miles　off　the　east　coast

of　Australia。　　Multitudes　of　the　islands　in　the　Pacific　are　either

reefs　themselves；　or　are　surrounded　by　reefs。　　The　Red　Sea　is　in

many　parts　almost　a　maze　of　such　reefs；　and　they　abound　no　less　in

the　West　Indies；　along　the　coast　of　Florida；　and　even　as　far　north

as　the　Bahama　Islands。　　But　it　is　a　very　remarkable　circumstance

that；　within　the　area　of　what　we　may　call　the　〃coral　zone；〃　there

are　no　coral　reefs　upon　the　west　coast　of　Ameri