the formation of vegetable mould-第4章

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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　indifference　to　my　breath　whilst　I　chewed　some　tobacco；　
and　while　a　pellet　of　cotton…wool　with　a　few　drops　of　millefleurs　
perfume　or　of　acetic　acid　was　kept　in　my　mouth。　　Pellets　of　cotton…
wool　soaked　in　tobacco　juice；　in　millefleurs　perfume；　and　in　
paraffin；　were　held　with　pincers　and　were　waved　about　within　two　or　
three　inches　of　several　worms；　but　they　took　no　notice。　　On　one　or　
two　occasions；　however；　when　acetic　acid　had　been　placed　on　the　
pellets；　the　worms　appeared　a　little　uneasy；　and　this　was　probably　
due　to　the　irritation　of　their　skins。　　The　perception　of　such　
unnatural　odours　would　be　of　no　service　to　worms；　and　as　such　timid　
creatures　would　almost　certainly　exhibit　some　signs　of　any　new　
impression；　we　may　conclude　that　they　did　not　perceive　these　
odours。

The　result　was　different　when　cabbage…leaves　and　pieces　of　onion　
were　employed；　both　of　which　are　devoured　with　much　relish　by　
worms。　　Small　square　pieces　of　fresh　and　half…decayed　cabbage…
leaves　and　of　onion　bulbs　were　on　nine　occasions　buried　in　my　pots；　
beneath　about　0。25　of　an　inch　of　common　garden　soil；　and　they　were　
always　discovered　by　the　worms。　　One　bit　of　cabbage　was　discovered　
and　removed　in　the　course　of　two　hours；　three　were　removed　by　the　
next　morning；　that　is；　after　a　single　night；　two　others　after　two　
nights；　and　the　seventh　bit　after　three　nights。　　Two　pieces　of　
onion　were　discovered　and　removed　after　three　nights。　　Bits　of　
fresh　raw　meat；　of　which　worms　are　very　fond；　were　buried；　and　were　
not　discovered　within　forty…eight　hours；　during　which　time　they　had　
not　become　putrid。　　The　earth　above　the　various　buried　objects　was　
generally　pressed　down　only　slightly；　so　as　not　to　prevent　the　
emission　of　any　odour。　　On　two　occasions；　however；　the　surface　was　
well　watered；　and　was　thus　rendered　somewhat　compact。　　After　the　
bits　of　cabbage　and　onion　had　been　removed；　I　looked　beneath　them　
to　see　whether　the　worms　had　accidentally　come　up　from　below；　but　
there　was　no　sign　of　a　burrow；　and　twice　the　buried　objects　were　
laid　on