44
_
THE ‘BI'OLOGY OF FISHES
_
'Covered—With mucus, derived probably from the cells lining
.
the ,_oviduct, and .in this way the eggs or =egg-masses become
_
adhesive to whatever they mayf_all upon.
_
The Perch and
J
-
other Freshwater shes lay strings of eggs which become
:en‘tangled on the water-plants. In other cases the eggs
simply remain in a dump together on the bottom, but in the
F reg—sh the mucus mass oats on the surface. Sometimes
the outer layer of the egg-shell (chorion) bursts on_coming
into contact with water and rollsi up at one end, as in"thé
Smelt and Gobies', to become an organ of attachment.
Or
the outer layer Wrinkles up in various ways and may be
_
thrown out into long laments, Which become attached as
they harden to the drifting or xed seaweed, as in the
Flying—sh and Garsh (Fig. 13“, 3). In Dog—shes and Rays
(Pl. V) the brous capsule isformed already in the oviduct,
like the egg—shell of the
“the long tendrils at the
_
c0rners curl found the seaweed,£bi the
simply
…;buried in the Sand
capsules
on the beach—as mèrmaids’ purSes, bÏut as_a
qÇuite‘empty.
;
-
Ü
-
;
,
,
These—are Sometimescalled adaptations, in their various
-wàys,*ad—it is,[sigriicat‘ that the: -egg-capsuleS Of the
‘
'Chimæridæand of most of the Rays, do
not have’t—he attaching tendrils. But the purposes usually
ascribed toîthe special adaptations become—mutuallyÿ_contræ
'
';dictbry_ when ,we—take all cases j-i1it0 "consideration, _s’of-t—hat
'
advantages-are ,pur"e1ÿ= 'hyÿothecàlr
.
.Thùs =
_
-of'*theajFrog—_sh aœ a jhindrance to the
,
free "deVelopmentgîîof the young fryîanda probably account for
its
structural abnormalities .
any “case, where . a
'
not fai—l‘to admire
1
.
_.
:.
‘
…
Fishesças a “rule—gare11niÏs'eXuàl,—mesomevery interesting
Î
»
‘eXceptions‘î—occur-Ï.æ
the Cod, Ling,
"Màckèrel,
Occasionally beenfoùnd With
.
—
xboth kinds of sexual—organs in one individual. SOmepof. the
_Sea—Perches ,(Sefranidæ) a're constantly'=hermaphrodit6.and
s‘<älf=fettilising.
In the Daurade