THE DEVELOPMENT OF FISHES
73
the pectoral region (Fig.
5 m). These have funnel—shaped
outlets, or rather inlets, and Williamson has observed the -
passage of small bodies
pores into the gut
The latter possesses a” number of ne cilia, which vibrate
from before backwards and thus *convey
”the
perivitelline uid through the gut and out by
_
Î
in the region of the future anus. Williamson has also
'
observed in” one form (Trachinus), that in the later stages .
there is a prolongation of the gut forward which divides
into two branches, one opening dorsallÿ on the head, the
other ventrally.
.
-.
;
’
As the uid thus obtained from the perivitelline space
soaks through the embryonic tissues, the embryos probably
obtain most of their oxygenin this way. ' It is pOssible” that
the yolk of these pelagic forms contains a large proportion
of dissolved organic substances, and thatthese reach the
tissues by means of the heart and loose vascular system
instead of through the gut. Inthe later embryoniC stages
_
the latter is shut off from the yolk (eXcept perhaps in"thè
:
,
_
.
,
-
”
.
Another important feature in these embryo‘è is the
presence of what appears to be an external excretoryisystem;
The kidney (pronephros) does not develop until theembryo
hatches out, butlorigbeforeïthis small papillæ withprojecting
tubules have appeared along each side of the body (Fig. 13€, 4”);
‘
These were formey.taken to be mucus =canals; bûttheyàr‘e‘
.
in all probability eXcretoryorganS'.'
'
”'.
_
—
These curious phenomena in the
life of the
Teleosts “can perhaps be interpreted in the following way.
'
The master activities, muscle and nerve, are
'
_
but there is Confusion in the
.”
be the
food— _’
-
supply, the
“
organs are of
of the interior; «That thæC’?œÿëÿÿ
*
apparent—and
_
is; imperfècy
,
and ”co—ordiation—; An 5 mœrestmg :thifg
.
‘ÏSf ' the” light— they
Ï