88
_
'
THE SEAS
—
‘
’
a similar life—history to that-just described for our eel, with
_
the only difference that the spawning ground is slightly to the
west of that 'of the European eel, and the leaf—shaped
larvætake only one, instead of three years before they are
'
ready to ascend. the American streàms as typical elvers .
(Plate 3 5).
.
difference in the life—histories of the European andî
American eels is of great interest in showing the Speeding
‘
up or slowing down of development to suit the environment., %
If the larvæ of the European eel took only one year to reach
metamôrphosis they would still be far from their destination
on the European Coasts, when they had assumed the shape
at
they nôrmally , ascend the rivers ; while the a
,
American eels by a reduction of the period of larval existence
'
are ready for metamorphosis by the time they have aived__,
at the American %coaS'ts.»
_.
,
,
.
A
reversed, lite—history is
the Atlàhticsalhidn (S‘ale salut). In the case of this
while the adults undefgo_ most of their growth in the‘sea,-,
'
they move up into the rivers to
their eggs.
The youngl
live
two or three years in the fresh water before m1gratmg
,
d'oWn to the open sea to feëd on the
foOd supplles
available there and to
that very great growth
dîStîêguishes ËhemîrQm—theîr relativesthé
Who.
.
lives in thé—rivets:
,
‘
.
'
can
be seen that, because of
journeys carried
_
ith€ area of théiï‘ïdiStributiÔn
at -.rdier‘cäntijtihaesg
year? and be -_ rather w1despreadr
-
:1s;oticéabieg rin
of the world
_
,
quitega
spëäè,jsj{
.
‘
ofshes
î’oî = course
m
t1da1