_
ADAPTATION
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2775
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cells surrounding the=,capillaries or small blood vessels in,
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the lining membrane ”of the sac, and enable the sh toin'—
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crease
of decrease the amount of the gasesin_ the reservoir, ,
but the reabsorption, is so veryîslow that it does not perm‘iÈof rapid changes of, level. _.jExperime'ts ;-have
that a sh—may be asphyxîated,thoughthe air.—bladder still
contains a cosiderable amount of oxygen.
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In. some cases, particularly among:the
Sciænoids—freShwater and ”marine
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ub_-_
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—
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_' .— FIG.-'
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a.b,
With
eätéÂf
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sions; v.ç.,
Column ; ‘1ÿ,. liVér' ;
mesentery
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former physostom‘e, the
amount
gas_taken orsecreted into therreservoiris so great that side
were, are developed in all direc—
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of the body and even roundthe—
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70): In; many Ways
,
remarkgbl@ asthe large air—sacs of birds, WhatusethË—Y
maÿfbe to the
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rifsi_Ï_feeî1@1ièy.çm en“croae11
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the bodY—s the
dëYdOP€d
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tions_.to
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just above the 5386 Of: the
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behmd
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