FISHES
THE WEB OF LIFE
ilè8'5îëï
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of the same materials, and the differenceï'ïalso, expresses:
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itself in the physicalbalance or proportions. ._ As a rule, the
difference persists throughout life, yet the essential identity
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of the materials _is
strange ways, by
various forms of hermarïhroditisrandthè
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sex to another.
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This theory of the phÿsiological distinction between-the
sexes, With thejWealth of evidence in its support
forWard by the authors mentioned, has been pushed “seme— ‘
What into the background by the interest taken in »Mendel’s
laws of herçdity and the chromosome theory of
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*
have led to fruitful
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ingçiher branches, they havenot been takenup to any
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eXtentïin. the study of shes. Here the natural conditions
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,
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are all
exact investigations, and Where articial
cultures have—"‘ been
as in Johs.
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experiments referred to in ;a
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have been rather;
the Ï,Mendelian,
,
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ln'additidn;to the ë'vi'denœmfavourofthephys1oîoglcal : f
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…
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dt…gth…nghf u ntf
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removedfromtheshes
be*even.
latter—5,Ï
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,
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N ermally,'
theory of
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equalpropoft—ion at birth
—males_-andfemales, ; Yîu‘ng',‘ in
,
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his
found’that tadpoles left-to*thn—“'
.
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selves tended to give such- proportioi1s, but if fed
“
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n0utishi—ng materials, beef, sh, and frog—esh, the pro,—'
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portion of females was greatly increased. -This result was
’ _
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expla1nedfrom the basis that tadpoles are really herta—
_
: phrod1testobegmwith or pass through a _hermaphrçdite ;
_
,
andth1s1s possibly true of_all
But Yung
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didi lnot=pâÿafëuîëien—t—aaattention-tOi the .mortalitr"'amQng his :
have been differential—,
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R._Hertwigï(1:912):haS'
eXperi,
ments; .
he
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