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f>i O F THE e y e s IN F i S H E S.
I cannot conclude without obferving the probability, that attention to the
denfity, ihape, refracting powers, and conne£tion of the humours of the eyes of
animals, may lead to the ftill farther improvement of optical inftruments.
C H A P T E R XI I .
ANATOMY of the SE P IA LOLIGO.
' " " 1 ^ 0 tliis account of the itructure of fiflies, I ihall fubjoin a defcription of
JL that of the Sepia Loligo; which I have found not lefs remarkable in its
internal ftructure than in its external ihape. By moil: authors it has been ranked
among the fiilies; by Linnsus it has been placed among the worms; but perhaps
it may moil juflly be coniidered as a link conne£Ung thefe two clafles of
animals.
T h e fepia loligo, which wants fins, has a triangular-ihaped tail (fee Tab. XLI.
fig. I. A A), and a hollow conical-lhaped mufcular ilieath, which inclofes its
thoracic and abdominal vifcera; reaching from its throat, where it is open and
admits the fea-water freely, to its tail, where it is ihut. This ilieath cut open
is reprefented at B B.
Near the mouth of the great ilicath there is another ficiliy conical funnel C,
wide behind and narrow beSre..
The fepia I laft diifecled had ten arihs D-D D , &c. with a great number of
cups E E E on each; by means of which it fixes itfelf to a rock; and with a
beak F, like that of a parrot, it breaks the ihells of the fea-worms on which it
feeds.
From the mouth the cefophagus G G fig. 3. runs ilraight down, covered behind
by its principal bone, or os fepiae, to end in a very mufcular ilomach H,
fig. I. fituated near the tail.
From the fore part of the fiomach, very near its cardia, the intcftinal canal, I,
begins; and after making a very few turns, ends in the re£tum KK, which runs
ftraight upwards on the fore part of the liver, and opens about the root of the
fleihy funnel C.
The liver M M is of great fize, and is fituated lengthwife on the fore fide of
the cefophagus.
On the fore fide of the liver, between it and the rc6tum, the ink-bag N is
fituated, tied to both. This bag is of a conical ihape, and of confiderable fize.
T h e
A N A T O M Y OF TKE S E P I A LOLIGO.
T h e duct from it, O, runs upwards between the liver and redtum, parallel with
the re£tum; into which, very near the anus, it difcharges itfelf.
As I did not obferve any other bladder conneded with the liver, I fuppofe
that the ink is the gall of this animal; yet while I was dctaching the ink-bag
and its d u d from the liver, I did not obferve that any gall-dufts were cut, nor
could I perceive, on fqueezing the hver or ink-bag, that any gall or ink was effufed.
Still, however, confidering the fituation and connection of the ink-bag,
this is perhaps not an improbable conjeClure. If fo, we are led a itep farther;
I mean, that as in this animal the bile does not ferve any of the purpofes commonly
alTigned to it, but is thrown out merely to affift the animal in making its
cfcapc, tliere is fome reafon to fufped, that one principal ufe of the liver may
be to drain off from the conftitution fome matter that is hurtful to it, or that
the bile is an excrementitious liquor.
Notwithftanding the great fize of the liver, I did not obferve any organ analogous
to the fpleen.
When we review the parts that have been defcribed, it feems propable that
the animal may puila its body forwards by the motion of its tail. But if the tail
is at reft, and the large outer flieath ftrongly and fuddenly contracted, the reaiStion
of the water within the ilieath will throw the whole body of the animal
backwards, whilit, at the fame inftant, the ink will be tlirown out of the bag,
and perhaps direded and thrown with itill greater force by the adtion of the mufcular
funnel C.
- If the tail be directed upwards, it is plain that the animal may, by fuch an
exertion, jump upwards out of the water, and ftill more readily make an efcape.
f r om its enemy.
Between tlie abdominal bowels and tlae back-bone I obfervcd a large thincoated
bag P, which in the firft fepia 1 examined was empty, and feemed to refemble
the fwimming-bladder of fiilies: but in orliers I dirtcitcd afterward, I
found it filled with a watery Jiquor, and a pafiTage or duct into it from a
glandular-looking organ; from which I fuppofe it to be the bladder of urine (¿).
On the under fore part of the liver and ink-bag, I remarked a glandularlooking
organ LL, confifting of a number of minute lobes; which I fufpedted
to be the ovarium of this animal.
In another larger fepia, I found a confiderable fac, with a large and long du<5t
f r om it, which terminated near the anus; and from which, on a flight preflure
of the fac, vermiform bodies were difcharged (2). Whether thefe are portions
of the organs of generation, which, after fome degree of putrefadtion, were detachcd
in this tender animal by flight preflure; or whether thefe bodies are naturally
difcharged in the produdion of the young, future obfcrvation muft de^
tcrmine.
The gills or lungs of this animal arc two conical-iliaped bodies one
fixed
(/.) See Tab. XLII. PQRS.
(0 S« Tab. XLII. MNO, and two figuiei at the f.Jeof the Tabli.
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