178
_
THE BIOL.GY OF FISHES
_’
.…degree to the laws of chance:occurrences. Such a
agreement has not been observed in the case,:9fotherspecies,'É _;f
.
mostly coastal.
and one is tempted towards
conclusion, that the conditions out in the Atlantic are more
evenly balanced and more uniform than those nearer
coast.
__
.
,
l'?
The precise agreement of the observed curve With the
-
normal curve can be seenfr0m the calculation of the third
.
-
.
-
2(æ3)
…!
moment
m
a
Similar manner as before
(&
If
the agreement is perfect, this value should be ‘equal to o.
'
Ë(x4)
_
_
The ;_-fourth moment
(,84
=
shows
the
eXtremesmeet the abscissa graduälly
or at a sharp
angle(B4<3) f In the case of the observed
fè;
'
Düncker hasobtaihed the values B3= —— 000244
j
and B4äa°03-goi.,
represent the closest agreement
between observed variations and the normal
Chance.
Occiurences'yet discovered. If the variability came from
the
as some think, then this agreement With the
nor-mal
be the same for all Species
Sinœ_this is far from being the case, we are obliged to think
,…
that the Outer conditions are responsible
:
Sometimes, it istrue, the obServedfrequencies
more to othertypes of probability curves,
types
but fôr practical purposes; sofarasthevanaüon of
?
is
itis bettertoassumethatthefrequenc1es
_'iÏ$hëüÏd‘îbé
'
Th1$dlrëctsourattentlOïî5“fÏ’d'le necessify ,Î '
50;f?<äbtàînis
isafrom— thesan‘œ
:plaœand t1meWeknowthat Species. va1yfromone
locahtyto anotherand,1f the material is composed of
the resultant
is ; "Î
almost certam to _be
Again,
L'
; thoughobtalned from £__thé}same locality may
=:Ê.
fndd1fmdtygp g thubn
have to besortedout