76
'
THE B—I‘OLOGY OF FISHES
but little yolk, but it is kept in intimate connection with the
nourishing uids of the mother. And the
“
laura,” when it
_remerges, is complete in all its parts
and organs;
what
follows we may call growth rather than development, such
as weSee in the Teleosts.
_
The development of certain deep—sea T eleosts, which
.
have come from advanced or specialised types, is worthy of
a special note. Trachypterus, for example, lives at considerable depths, but the eggs when spawned rise into the upper
layers, though not to the surface. The egg then swells,
a perivitelline space is formed and the embryo thus obtains
more
space.
Hece the development is rapid and the
muscular system again is early formed and comes into use
(Fig. 13, 6) ; then the various organs follow in succession,
—
system, ns, even the peculiar coil of the gut,
until the embryo‘iS a complete miniature of the adult. The
eyes of the embryo when rst brought to the surface are
.
,
large and protruding
that
reacts to differences of pressure, but they 'becomenormal
‘
after .a…few days.
__
.
'
_
'
:
'
.
1
»
=
The SimpleSt and most primitive kind of sh larva can
be picturedfrom
of the larvæï of the Clupeids
and their allies,
Herring, Sprat, Albula
'
and Chirocentrus.
The characters of such a larva are as
,
follows (Fig. 18, 1; p. 85).
-—
.fr
'
_
There is a uniform segmentation of the body (myomeres)
'
from'head to tail. The notochord is very large, occupyi’ng
'
'
the body, ”and is uhicellular or
‘
_
b1cellular (F1g17,1)wherem laterfŒms it becomes multi—
'
_
cellular.
!. { .The;_.nerÿe'cord-lies immediately
'
under the dorsal
_
_
margin “of_;thç; bodÿ.;—The straight gut, closed anteriorly,
”the {whole length of the body right
tail,
'
indicatihg— the" nearest known approximation to "the
'
:
neurenterié canal. The just hatched embryo has no mouth,
”n_O
no kidrieys ;: it
breatheor feed
'
Î
_
like a sh.head is a “membranouS sWelling in front of
-'
the myomeres andfthe.eyes,are
'
:
;W‘Ïth‘?f
aszÿet‘
'
THE B—I‘OLOGY OF FISHES
but little yolk, but it is kept in intimate connection with the
nourishing uids of the mother. And the
“
laura,” when it
_remerges, is complete in all its parts
and organs;
what
follows we may call growth rather than development, such
as weSee in the Teleosts.
_
The development of certain deep—sea T eleosts, which
.
have come from advanced or specialised types, is worthy of
a special note. Trachypterus, for example, lives at considerable depths, but the eggs when spawned rise into the upper
layers, though not to the surface. The egg then swells,
a perivitelline space is formed and the embryo thus obtains
more
space.
Hece the development is rapid and the
muscular system again is early formed and comes into use
(Fig. 13, 6) ; then the various organs follow in succession,
—
system, ns, even the peculiar coil of the gut,
until the embryo‘iS a complete miniature of the adult. The
eyes of the embryo when rst brought to the surface are
.
,
large and protruding
that
reacts to differences of pressure, but they 'becomenormal
‘
after .a…few days.
__
.
'
_
'
:
'
.
1
»
=
The SimpleSt and most primitive kind of sh larva can
be picturedfrom
of the larvæï of the Clupeids
and their allies,
Herring, Sprat, Albula
'
and Chirocentrus.
The characters of such a larva are as
,
follows (Fig. 18, 1; p. 85).
-—
.fr
'
_
There is a uniform segmentation of the body (myomeres)
'
from'head to tail. The notochord is very large, occupyi’ng
'
'
the body, ”and is uhicellular or
‘
_
b1cellular (F1g17,1)wherem laterfŒms it becomes multi—
'
_
cellular.
!. { .The;_.nerÿe'cord-lies immediately
'
under the dorsal
_
_
margin “of_;thç; bodÿ.;—The straight gut, closed anteriorly,
”the {whole length of the body right
tail,
'
indicatihg— the" nearest known approximation to "the
'
:
neurenterié canal. The just hatched embryo has no mouth,
”n_O
no kidrieys ;: it
breatheor feed
'
Î
_
like a sh.head is a “membranouS sWelling in front of
-'
the myomeres andfthe.eyes,are
'
:
;W‘Ïth‘?f
aszÿet‘