,
{: ff
OF msnss
;
.
‘
marked off according
depths over which the larvâélî
l
_
live when their Structures are being formedi '.
Ï
that the
was a single-species to begin with,—
*
the Separation would come from the larvae settling do'wn at
different depths, the range of depths being from 0 to some]
;
500 fathorns.
In the case of A. latema,
have a modern
_
species which is separating up in this way.
Similarly,
’— if
—
thespaVvning time of a species is spread over several months”
_
_ofthe Year, the conditions are again present for the breaking
"
_
'
the species. ,
?.
.
,
»
.
'
.
Ÿ It is not only through small variations, however, that shes -
':
'
have become differe‘ntiated from one another; There is abun'
Ï *}
':dant'f evidence that abrupt changes, mutations, have been
*
fof_{ÿfrequèm cecilrrenCe, T he transformation of a normal
;
larVà{itô
Pipe=sh;or a“Plecätognathis a muta—
,
Tele0sts have probably arisen
_
in thièî way and—not »by gradual variation, We have seen
in Chapter V, how in'one formof balance the anal n has
,
crept forwards until the 'venti-al ns could
' _
"*
’
develop
In StromateoideS- the ventrals are
Ï' wellêdeveloped toi begin With but-later Ïdiscarded, and the ;.
the peotoral ns
phen0menon
beenfoùnd to-arise_£rom
5 ' of=the
L
-
_
.
_
:
shapesofîhemwthasthebaïance0ftheb0dychangœare
:.
Phafyngeal
5—;_j
—Ïjïj
is of theÏsamenthuœ.—, Lasÿ, the;
'_
of..‘thefgutl‘isîanatural :conéeduèn‘ce of its
_
but
:i‘r—hpo‘rtant, mutations, the? '
:
Valves andtthe' loss of.
,
_
ahmentary
—
__'__5_
’
=
.