with　hammer　and　chisel；　at　the　expense　of　much　dirt　and　patience；
  for　the　moment　it　is　touched　it　contracts　deep　into　the　rock；　and
  all　that　is　left　of　the　daisy　flower；　some　two　or　three　inches
  across；　is　a　blue　knot　of　half　the　size　of　a　marble。　　But　it　will
  expand　again；　after　a　day　or　two　of　captivity；　and　will　repay　all
  the　trouble　which　it　has　cost。　　Troglodytes　may　be　found；　as　I　have
  said　already；　in　hundreds　at　Hastings；　in　similar　situations　to
  that　of　Bellis；　its　only　token；　when　the　tide　is　down；　being　a
  round　dimple　in　the　muddy　sand　which　firs　the　lower　cracks　of
  rocks。
  But　you　will　want　more　than　these　anemones；　both　for　your　own
  amusement；　and　for　the　health　of　your　tank。　　Microscopic　animals
  will　breed；　and　will　also　die；　and　you　need　for　them　some　such
  scavenger　as　our　poor　friend　Squinado；　to　whom　you　were　introduced
  a　few　pages　back。　　Turn；　then；　a　few　stones　which　lie　piled　on　each
  other　at　extreme　low…water　mark；　and　five　minutes'　search　will　give
  you　the　very　animal　you　want；　…　a　little　crab；　of　a　dingy　russet
  above；　and　on　the　under　side　like　smooth　porcelain。　　His　back　is
  quite　flat；　and　so　are　his　large　angular　fringed　claws；　which；　when
  he　folds　them　up；　lie　in　the　same　plane　with　his　shell；　and　fit
  neatly　into　its　edges。　　Compact　little　rogue　that　he　is；　made
  especially　for　sidling　in　and　out　of　cracks　and　crannies；　he
  carries　with　him　such　an　apparatus　of　combs　and　brushes　as　Isidor
  or　Floris　never　dreamed　of；　with　which　he　sweeps　out　of　the　sea…
  water　at　every　moment　shoals　of　minute　animalcules；　and　sucks　them
  into　his　tiny　mouth。　　Mr。　Gosse　will　tell　you　more　of　this　marvel；
  in　his　〃Aquarium；〃　p。　48。
  Next；　your　sea…weeds；　if　they　thrive　as　they　ought　to　do；　will　sow
  their　minute　spores　in　millions　around　them；　and　these；　as　they
  vegetate；　will　form　a　green　film　on　the　inside　of　the　glass；
  spoiling　your　prospect：　　you　may　rub　it　off　for　yourself；　if　you
  will；　with　a　rag　fastened　to　a　stick；　but　if　you　wish　at　once　to
  save　yourself　trouble；　and　to　see　how　all　emergencies　in　nature　are
  provided　for；　you　will　set　three　or　four　live　shells　to　do　it　for
  you；　and　to　keep　your　sub…aqueous　lawn　close　mown。
  That　last　word　is　no　figure　of　speech。　　Look　among　the　beds　of　sea…
  weed　for　a　few　of　the　bright　yellow　or　green　sea…snails　（Nerita）；
  or　Conical　Tops　（Trochus）；　especially　that　beautiful　pink　one
  spotted　with　brown　（Ziziphinus）；　which　you　are　sure　to　find　about
  shaded　rock…ledges　at　dead　low　tide；　and　put　them　into　your
  aquarium。　　For　the　present；　they　will　only　nibble　the　green　ulvae；
  but　when　the　film　of　young　weed　begins　to　form；　you　will　see　it
  mown　off　every　morning　as　fast　as　it　grows；　in　little　semicircular
  sweeps；　just　as　if　a　fairy's　scythe　had　been　at　work　during　the
  night。
  And　a　scythe　has　been　at　work；　none　other　than　the　tongue　of　the
  little　shell…fish；　a　description　of　its　extraordinary　mechanism
  （too　long　to　quote　here；　but　which　is　well　worth　reading）　may　be
  found　in　Gosse's　〃Aquarium。〃　（32）
  A　prawn　or　two；　and　a　few　minute　star…fish；　will　make　your　aquarium
  complete；　though　you　may　add　to　it　endlessly；　as　one　glance　at　the
  salt…water　tanks　of　the　Zoological　Gardens；　and　the　strange　and
  beautiful　forms　which　they　contain；　will　prove　to　you　sufficiently。
  You　have　two　more　enemies　to　guard　against；　dust；　and　heat。　　If　the
  surface　of　the　water　becomes　clogged　with　dust；　the　communication
  between　it　and　the　life…giving　oxygen　of　the　air　is　cut　off；　and
  then　your　animals　are　liable　to　die；　for　the　very　same　reason　that
  fish　die　in　a　pond　which　is　long　frozen　over；　unless　a　hole　be
  broken　in　the　ice　to　admit　the　air。　　You　must　guard　against　this　by
  occasional　stirring　of　the　surface；　or；　as　I　have　already　said；　by
  syringing　and　by　keeping　on　a　cover。　　A　piece　of　muslin　tied　over
  will　do；　but　a　better　defence　is　a　plate　of　glass；　raised　on　wire
  some　half…inch　above　the　edge；　so　as　to　admit　the　air。　　I　am　not
  sure　that　a　sheet　of　brown　paper　laid　over　the　vase　is　not　the　best
  of　all；　because　that；　by　its　shade；　also　guards　against　the　next
  evil；　which　is　heat。　　Against　that　you　must　guard　by　putting　a
  curtain　of　muslin　or　oiled　paper　between　the　vase　and　the　sun；　if
  it　be　very　fierce；　or　simply　（for　simple　expedients　are　best）　by
  laying　a　handkerchief　over　it　till　the　heat　is　past。　　But　if　you
  leave　your　vase　in　a　sunny　window　long　enough　to　let　the　water　get
  tepid；　all　is　over　with　your　pets。　　Half　an　hour's　boiling　may
  frustrate　the　care　of　weeks。　　And　yet；　on　the　other　hand；　light　you
  must　have；　and　you　can　hardly　have　too　much。　　Some　animals
  certainly　prefer　shade；　and　hide　in　the　darkest　crannies；　and　for
  them；　if　your　aquarium　is　large　enough；　you　must　provide　shade；　by
  arranging　the　bits　of　stone　into　piles　and　caverns。　　But　without
  light；　your　sea…weeds　will　neither　thrive　nor　keep　the　water　sweet。
  With　plenty　of　light　you　will　see；　to　quote　Mr。　Gosse　once　more；
  （33）　〃thousands　of　tiny　globules　forming　on　every　plant；　and　even
  all　over　the　stones；　where　the　infant　vegetation　is　beginning　to
  grow；　and　these　globules　presently　rise　in　rapid　succession　to　the
  surface　all　over　the　vessel；　and　this　process　goes　on
  uninterruptedly　as　long　as　the　rays　of　the　sun　are　uninterrupted。
  〃Now　these　globules　consist　of　PURE　OXYGEN；　given　out　by　the　plants
  under　the　stimulus　of　light；　and　to　this　oxygen　the　animals　in　the
  tank　owe　their　life。　　The　difference　between　the　profusion　of
  oxygen…bubbles　produced　on　a　sunny　day；　and　the　paucity　of　those
  seen　on　a　dark　cloudy　day；　or　in　a　northern　aspect；　is　very
  marked。〃　　Choose；　therefore；　a　south　or　east　window；　but　draw　down
  the　blind；　or　throw　a　handkerchief　over　all　if　the　heat　become
  fierce。　　The　water　should　always　feel　cold　to　your　hand；　let　the
  temperature　outside　be　what　it　may。
  Next；　you　must　make　up　for　evaporation　by　FRESH　water　（a　very
  little　will　suffice）；　as　often　as　in　summer　you　find　the　water　in
  your　vase　sink　below　its　original　level；　and　prevent　the　water　from
  getting　too　salt。　　For　the　salts；　remember；　do　not　evaporate　with
  the　water；　and　if　you　left　the　vase　in　the　sun　for　a　few　weeks；　it
  would　become　a　mere　brine…pan。
  But　how　will　you　move　your　treasures　up　to　town？
  The　simplest　plan　which　I　have　found　successful　is　an　earthen　jar。
  You　may　buy　them　with　a　cover　which　screws　on　with　two　iron　clasps。
  If　you　do　not　find　such；　a　piece　of　oilskin　tied　over　the　mouth　is
  enough。　　But　do　not　fill　the　jar　full　of　water；　leave　about　a
  quarter　of　the　contents　in　empty　air；　which　the　water　may　absorb；
  and　so　keep　itself　fresh。　　And　any　pieces　of　stone；　or　oysters；
  which　you　send　up；　hang　by　a　string　from　the　mouth；　that　they　may
  not　hurt　tender　animals　by　rolling　about　the　bottom。　　With　these
  simple　precautions；　anything　which　you　are　likely　to　find　will　well
  endure　forty…eight　hours　of　travel。
  What　if　the　water　fails；　after　all？
  Then　Mr。　Gosse's　artificial　sea…water　will　form　a　perfect
  substitute。　　You　may　buy　the　requisite　salts　（for　there　are　more
  salts　than　〃salt〃　in　sea…water）　from　any　chemist　to　whom　Mr。　Gosse
  has　entrusted　his　discovery；　and；　according　to　his　directions；　make
  sea…water　for　yourself
  One　more　hint　before　we　part。　　If；　after　all；　you　are　not　going
  down　to　the　sea…side　this　year；　and　have　no　opportunities　of
  testing　〃the　wonders　of　the　shore；〃　you　may　still　study　Natural
  History　in　your　own　drawing…room；　by　looking　a　little　into　〃the
  wonders　of　the　pond。〃
  I　am　not　jesting；　a　fresh…water　aquarium；　though　by　no　means　as
  beautiful　as　a　salt…water　one；　is　even　more　easily　established。　　A
  glass　jar；　floored　with　two　or　three　inches　of　pond…mud　（which
  should　be　covered　with　fine　gravel　to　prevent　the　mud　washing　up）；
  a　specimen　of　each　of　two　water…plants　which　you　may　buy　now　at　any
  good　shop　in　Covent　Garden；　Vallisneria　spiralis　（which　is　said　to
  give　to　the　Canvas…backed　duck　of　America　its　peculiar　richness　of
  flavour）；　and　Anacharis　alsinastrum；　that　magical　weed　which；
  lately　introduced　from　Canada　among　timber；　has　multiplied；　self…
  sown；　to　so　prodigious　an　extent；　that　it　bid　fair；　a　few　years
  since；　to　choke　the　navigation　not　only　of　our　canals　and　fen…
  rivers；　but　of　the　Thames　itself：　　（34）　or；　in　default　of　these；
  some　of　the　more　delicate　pond…weeds；　such　as　Callitriche；
  Potamogeton　pusillum；　and；　best　of　all；　perhaps；　the　beautiful
  Water…Milfoil　（Myriophyllium）；　whose　comb…like　leaves　are　the
  haunts　of　numberless　rare　and　curious　animalcules：…　these　（in
  themselves；　from　the　transparency　of　their　circulation；　interesting
  microscopic　objects）　for　oxygen…breeding　vegetables；　and　for
  animals；　the　pickings　of　any　pond；　a　minnow　or　two；　an　eft；　a　few
  of　the　delicate　pond…snails　（unless　they　devour　your　plants　too
  rapidly）：　　water…beetles；　of　a