ECONOMY OF
BODY—J
123
still persistent among the shes; In many cases also the
epithelium is ciliated to help the food along. This
reminiscence of a primitive Character is common
the
_
_
Dipnoi (Protopterus) and the Ganoids‘,
; is possibly
connected With a slug—gish temperærient; butmore probably
they cannot help themselves and theifslriggishness Comes
-
from the retention of this and other primitive jch—aracters.
We can
at any rate, that a greater development of
musclé would react on the digestive
and _leadftd
increasing
to
dierentiatiOn Of
the various parts.
,
_—,
,
,
.
It is worth n0ting in this connection that the ÏClupeids,
Which begin as it Were at the very beginning of the sh
series, take their place in the adult condition among the most
highly organised. They are- active shes everywhere and
Show a variety of innovations, Which other shes and.- higher
animals haveturnedto special account. Not content With
turning part of the gullet into— a stomach (&), they have
{expanded the latter into a sigmoid exure, so:that the food
_
travelling
.
the
almost to where it
.
_Started ifroin,
have given up'Ï this
pecuhantywestlretam1t
:
'
'
,,
'
Thereisaconstr1ct10n,butno
_
leadswell—madeduodenum
,
"
‘
on itself in the
through slowly. It is just at this place“ that various important
glands ‘are developed and pour out their ferments
digestion of the food. Then follows a long thin intestine (1)
With numerous folds in the. mucous membrane for the
retention and absorption of the digested “brew.” There
is no large intestine or colon, the thin—walledgùt passes into
a short and muscular rectum, which opens out to the exteri0r;
_
In other Teleosts the1rectal open—ing is_‘_,.diSfèinct fromthe
urinogenital opening—_; in some Clupçid3,
etc., there are four
all together ina smgledepressmn
whichmay
Called, the begmnmgs
(a) {«
,
°
}
__
.aSOIC
in the! above “apparatus may;
ujust' be