the formation of vegetable mould-第3部分

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for　as　soon　as　the　light　fell　on　them；　they　withdrew　into　their　
burrows　with　almost　instantaneous　rapidity。　　This　occurred　perhaps　
once　out　of　a　dozen　times。　　When　they　did　not　withdraw　instantly；　
they　often　raised　the　anterior　tapering　ends　of　their　bodies　from　
the　ground；　as　if　their　attention　was　aroused　or　as　if　surprise　was　
felt；　or　they　moved　their　bodies　from　side　to　side　as　if　feeling　
for　some　object。　　They　appeared　distressed　by　the　light；　but　I　
doubt　whether　this　was　really　the　case；　for　on　two　occasions　after　
withdrawing　slowly；　they　remained　for　a　long　time　with　their　
anterior　extremities　protruding　a　little　from　the　mouths　of　their　
burrows；　in　which　position　they　were　ready　for　instant　and　complete　
withdrawal。

When　the　light　from　a　candle　was　concentrated　by　means　of　a　large　
lens　on　the　anterior　extremity；　they　generally　withdrew　instantly；　
but　this　concentrated　light　failed　to　act　perhaps　once　out　of　half　
a　dozen　trials。　　The　light　was　on　one　occasion　concentrated　on　a　
worm　lying　beneath　water　in　a　saucer；　and　it　instantly　withdrew　
into　its　burrow。　　In　all　cases　the　duration　of　the　light；　unless　
extremely　feeble；　made　a　great　difference　in　the　result；　for　worms　
left　exposed　before　a　paraffin　lamp　or　a　candle　invariably　
retreated　into　their　burrows　within　from　five　to　fifteen　minutes；　
and　if　in　the　evening　the　pots　were　illuminated　before　the　worms　
had　come　out　of　their　burrows；　they　failed　to　appear。

From　the　foregoing　facts　it　is　evident　that　light　affects　worms　by　
its　intensity　and　by　its　duration。　　It　is　only　the　anterior　
extremity　of　the　body；　where　the　cerebral　ganglia　lie；　which　is　
affected　by　light；　as　Hoffmeister　asserts；　and　as　I　observed　on　
many　occasions。　　If　this　part　is　shaded；　other　parts　of　the　body　
may　be　fully　illuminated；　and　no　effect　will　be　produced。　　As　these　
animals　have　no　eyes；　we　must　suppose　that　the　light　passes　through　
their　skins；　and　in　some　manner　excites　their　cerebral　ganglia。　　It　
appeared　at　first　probable　that　the　different　manner　in　which　they　
were　affected　on　different　occasions　might　be　explained；　either　by　
the　degree　of　extension　of　their　skin　and　its　consequent　
transparency；　or　by　some　particular　incident　of　the　light；　but　I　
could　discover　no　such　relation。　　One　thing　was　manifest；　namely；　
that　when　worms　were　employed　in　dragging　leaves　into　their　burrows　
or　in　eating　them；　and　even　during　the　short　intervals　whilst　they　
rested　from　their　work；　they　either　did　not　perceive　the　light　or　
were　regardless　of　it；　and　this　occurred　even　when　the　light　was　
concentrated　on　them　through　a　large　lens。　　So；　again；　whilst　they　
are　paired；　they　will　remain　for　an　hour　or　two　out　of　their　
burrows；　fully　exposed　to　the　morning　light；　but　it　appears　from　
what　Hoffmeister　says　that　a　light　will　occasionally　cause　paired　
individuals　to　separate。

When　a　worm　is　suddenly　illuminated　and　dashes　like　a　rabbit　into　
its　burrowto　use　the　expression　employed　by　a　friendwe　are　at　
first　led　to　look　at　the　action　as　a　reflex　one。　　The　irritation　of　
the　cerebral　ganglia　appears　to　cause　certain　muscles　to　contract　
in　an　inevitable　manner；　independently　of　the　will　or　consciousness　
of　the　animal；　as　if　it　were　an　automaton。　　But　the　different　
effect　which　a　light　produced　on　different　occasions；　and　
especially　the　fact　that　a　worm　when　in　any　way　employed　and　in　the　
intervals　of　such　employment；　whatever　set　of　muscles　and　ganglia　
may　then　have　been　brought　into　play；　is　often　regardless　of　light；　
are　opposed　to　the　view　of　the　sudden　withdrawal　being　a　simple　
reflex　action。　　With　the　higher　animals；　when　close　attention　to　
some　object　leads　to　the　disregard　of　the　impressions　which　other　
objects　must　be　producing　on　them；　we　attribute　this　to　their　
attention　being　then　absorbed；　and　attention　implies　the　presence　
of　a　mind。　　Every　sportsman　knows　that　he　can　approach　animals　
whilst　they　are　grazing；　fighting　or　courting；　much　more　easily　
than　at　other　times。　　The　state；　also；　of　the　nervous　system　of　the　
higher　animals　differs　much　at　different　times；　for　instance；　a　
horse　is　much　more　readily　startled　at　one　time　than　at　another。　　
The　comparison　here　implied　between　the　actions　of　one　of　the　
higher　animals　and　of　one　so　low　in　the　scale　as　an　earth…worm；　may　
appear　far…fetched；　for　we　thus　attribute　to　the　worm　attention　and　
some　mental　power；　nevertheless　I　can　see　no　reason　to　doubt　the　
justice　of　the　comparison。

Although　worms　cannot　be　said　to　possess　the　power　of　vision；　their　
sensitiveness　to　light　enables　them　to　distinguish　between　day　and　
night；　and　they　thus　escape　extreme　danger　from　the　many　diurnal　
animals　which　prey　on　them。　　Their　withdrawal　into　their　burrows　
during　the　day　appears；　however；　to　have　become　an　habitual　action；　
for　worms　kept　in　pots　covered　by　glass　plates；　over　which　sheets　
of　black　paper　were　spread；　and　placed　before　a　north…east　window；　
remained　during　the　day…time　in　their　burrows　and　came　out　every　
night；　and　they　continued　thus　to　act　for　a　week。　　No　doubt　a　
little　light　may　have　entered　between　the　sheets　of　glass　and　the　
blackened　paper；　but　we　know　from　the　trials　with　coloured　glass；　
that　worms　are　indifferent　to　a　small　amount　of　light。

Worms　appear　to　be　less　sensitive　to　moderate　radiant　heat　than　to　
a　bright　light。　　I　judge　of　this　from　having　held　at　different　
times　a　poker　heated　to　dull　redness　near　some　worms；　at　a　distance　
which　caused　a　very　sensible　degree　of　warmth　in　my　hand。　　One　of　
them　took　no　notice；　a　second　withdrew　into　its　burrow；　but　not　
quickly；　the　third　and　fourth　much　more　quickly；　and　the　fifth　as　
quickly　as　possible。　　The　light　from　a　candle；　concentrated　by　a　
lens　and　passing　through　a　sheet　of　glass　which　would　intercept　
most　of　the　heat…rays；　generally　caused　a　much　more　rapid　retreat　
than　did　the　heated　poker。　　Worms　are　sensitive　to　a　low　
temperature；　as　may　be　inferred　from　their　not　coming　out　of　their　
burrows　during　a　frost。

Worms　do　not　possess　any　sense　of　hearing。　　They　took　not　the　least　
notice　of　the　shrill　notes　from　a　metal　whistle；　which　was　
repeatedly　sounded　near　them；　nor　did　they　of　the　deepest　and　
loudest　tones　of　a　bassoon。　　They　were　indifferent　to　shouts；　if　
care　was　taken　that　the　breath　did　not　strike　them。　　When　placed　on　
a　table　close　to　the　keys　of　a　piano；　which　was　played　as　loudly　as　
possible；　they　remained　perfectly　quiet。

Although　they　are　indifferent　to　undulations　in　the　air　audible　by　
us；　they　are　extremely　sensitive　to　vibrations　in　any　solid　object。　　
When　the　pots　containing　two　worms　which　had　remained　quite　
indifferent　to　the　sound　of　the　piano；　were　placed　on　this　
instrument；　and　the　note　C　in　the　bass　clef　was　struck；　both　
instantly　retreated　into　their　burrows。　　After　a　time　they　emerged；　
and　when　G　above　the　line　in　the　treble　clef　was　struck　they　again　
retreated。　　Under　similar　circumstances　on　another　night　one　worm　
dashed　into　its　burrow　on　a　very　high　note　being　struck　only　once；　
and　the　other　worm　when　C　in　the　treble　clef　was　struck。　　On　these　
occasions　the　worms　were　not　touching　the　sides　of　the　pots；　which　
stood　in　saucers；　so　that　the　vibrations；　before　reaching　their　
bodies；　had　to　pass　from　the　sounding　board　of　the　piano；　through　
the　saucer；　the　bottom　of　the　pot　and　the　damp；　not　very　compact　
earth　on　which　they　lay　with　their　tails　in　their　burrows。　　They　
often　showed　their　sensitiveness　when　the　pot　in　which　they　lived；　
or　the　table　on　which　the　pot　stood；　was　accidentally　and　lightly　
struck；　but　they　appeared　less　sensitive　to　such　jars　than　to　the　
vibrations　of　the　piano；　and　their　sensitiveness　to　jars　varied　
much　at　different　times。

It　has　often　been　said　that　if　the　ground　is　beaten　or　otherwise　
made　to　tremble；　worms　believe　that　they　are　pursued　by　a　mole　and　
leave　their　burrows。　　From　one　account　that　I　have　received；　I　have　
no　doubt　that　this　is　often　the　case；　but　a　gentleman　informs　me　
that　he　lately　saw　eight　or　ten　worms　leave　their　burrows　and　crawl　
about　the　grass　on　some　boggy　land　on　which　two　men　had　just　
trampled　while　setting　a　trap；　and　this　occurred　in　a　part　of　
Ireland　where　there　were　no　moles。　　I　have　been　assured　by　a　
Volunteer　that　he　has　often　seen　many　large　earth…worms　crawling　
quickly　about　the　grass；　a　few　minutes　after　his　company　had　fired　
a　volley　with　blank　cartridges。　　The　Peewit　（Tringa　vanellus；　
Linn。）　seems　to　know　instinctively　that　worms　will　emerge　if　the　
ground　is　made　to　tremble；　for　Bishop　Stanley　states　（as　I　hear　
from　Mr。　Moorhouse）　that　a　young　peewit　kept　in　confinement　used　to　
stand　on　one　leg　and　beat　the　turf　with　the　other　leg　until　the　
worms　crawled　out　of　their　burrows；　when　they　were　instantly　
devoured。　　Nevertheless；　worms　do　not　invariably　leave　their　
burrows　when　the　ground　is　made　to　tremble；　as　I　know　by　having　
beaten　it　with　a　spade；　but　perhaps　it　was　beaten　too　violently。

The　whole　body　of　a　worm　is　sensitive　to　contact。　　A　slight　puff　of　
air　from　the　mouth　causes　an　instant　retreat。　　The　glass　plates　
placed　over　the　pots　did　not　fit　closely；　and　blowing　through　the　
very　narrow　chinks　thus　left；　often　sufficed　to　cause　a　rapid　
retreat。　　They　sometimes　perceived　the　eddies　in　the　air　caused　by　
quickly　removing　the　glass　plates。　　When　a　worm　first　comes　out　of　
its　burrow；　it　generally　moves　the　much　extended　anterior　extremity　
of　its　body　from　side　to　side　in　all　directions；　apparently　as　an　
organ　of　touch；　and　there　is　some　reason　to　believe；　as　we　shall　
see　in　the　next　chapter；　that　they　are　thus　enabled　to　gain　a　
general　notion　of　the　form　of　an　object。　　Of　all　their　senses　that　
of　touch；　including　in　this　term　the　perception　of　a　vibration；　
seems　much　the　most　highly　developed。

In　worms　the　sense　of　smell　apparently　is　confined　to　the　
perception　of　certain　odours；　and　is　feeble。　　They　were　quite　
indifferent　to　my　breath；　as　long　as　I　breathed　on　them　very　
gently。　　This　was　tried；　because　it　appeared　possible　that　they　
might　thus　be　warned　of　the　approach　of　an　enemy。　　They　exhibited　
the　same　indiffere