The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1867-02-21

narrow systems. (ApplauSe')
THE FISHES PROPER.
In the infancy of our science, all the inhabit-
ants of the fresh water were called fishes, and
IL is only in proportion as we have become
acquainted with these structural differences,
that this class of fishes, embracing so much,
thus varied in structure and plan, has been
gradually referred to different classes VIII
now pass on to the fishes proper to those re-
representatives. of the fresh water which instruc-
ture resemble man, and which share with us
that plan of structure which is common to the
birds and reptiles and quadrupeds, as well as
to man and the fishes proper. II the time per-
mits shall close with a few remarks upon the
fresh water inhabitants OF the type OF the YER
tebrates, worms, and crustacea; but If not, l
shall defer my remarks upon those classes TO
my next lecture. feel somewhat embarrassed
to speak of fishes without saying something of
the fundamental differences which exist among
Them and that may better bring before you
the differences which characterize the diff
ferent groups of fishes, let me draw
the outlines of some of them, and point
out to you the permanent differences which
distinguish them. Suppose | take, first, our
trout. You perceive here that the head and
body run together so that there is hardly
distinct neck. That is a characteristic feature
of all fishes. 1t is only in the class of reptiles
that we begin to perceive the first indication
of the contraction between the head and body
which indicates the position of the neck.
What is characteristic of this type of fishes is
the position of the fin upon the back, which is
called the dorsal. There is q large fin at the
end of the tail, which may be cut square, as
in the fresh-water trout; which may be forked
as in the sea-tTout; or which may have its
upper end prolonged greatly, as in,sOme other
representatives of the family. This is the
caudal and that fin is the organ with which
these fishes impart to themselves an onward
motion.
POSITION AND USES OF THE FINS.
Striking right and left with the tail the body
| is propelled forward in consequence of this
| motion, and this motion is aided by the dorsal.
| This other fin under the tail is called the anal.
| When the fish strikes violently and raises that
| fin, the surface with which he strikes the
water is enlarged; but when he strikes gently
this fin is bent under the tail, and the surface
| with which he strikes the water is diminished
and the force with which he strikes being
| slight, the motion is comparatively feeble.
| The fin is the ventral. This is on the medal
| line of the body. There is one above, the
| dorsal, and one below the anal, and the eau
dal at the end of the body. The caudal in this
group of fishes is always semicircular that is,
| the upper half corresponds with the lower
| half. If the tail is cut square, then the two
| parts are about the same; and if it is forked,
then the upper part is of about the same
dimensions as the lower. 1t is rarely the case
that one of those parts is slightly longer than
the other, and it may be either the upper or
the lower. For instance, in the tlying-fsh
which comes very near this, we have the
lower lobe somewhat longer than the upper.
With this, the moment the fish emerges from
the water, it gives its last impulse by striking
violently to the right and left several
times in rapid succession. We have,
also, upon each side of the body
one on the right and one on the left those
fins which are near the head, which are, i'll
| fact, upon the sides of the chest, and which
are known by the name of the pectorals; and
these which are here, upon the lower sides of
the abdominal cavity, are known as the alb
dominal fins. In all the fishes of this group
we have the abdominal fin, half way between
| the pectoral and the anal fins. Now let us
compare with that a perch, q common yellow
| perch, as we have them in our fresh water.
Here (drawing) we have very different dor
sal; there are two, commonly large. We have
! the caudal comparatively small and feeble.
| We have the anal placed in about the same
position as in the trout, but it has strong
! spine in front sof the fin. Then we have the
pectoras placed here, and the ventrals, in
stead of occupying medal position, are placed
! just below the pectorals, and the front part of
the ventrals sustains a strong spine. You see
| at once what difference that makes. This
| first fin consists of strong spines, while the
| second fin consists of a number of rays which
| are divided and subdivided so that the whole
| fin is soft and tender while this is very hard
and priclly. So are the spines hare so are
| the spines there and on the sides of the head
| there are other spnes connected with the
bones of the head. But that is not all. Let
| us examine the mouth. Here the mouth is
very widely cleft, perhaps, but there are also
! perches in which the mouth is very widely
! cleft.
THE JAWS AND TEETH.
\ But the principal difference is that here, in
I the 'front.' the interior of the upper jaw is made
/ up of one bone, and the posteriOr part of the
upper jaw of anOher bone, which two bones are
! placed one i'll succession to the other, forming
| one arch, and both have teeth along their
| lower edge. These two bones are exactly the
same as those which form the upper margin
| of our own mouth. The anterior part of the
mouth is occupied by the cutting teeth; then
follow the eye teeth then the grinders. Now
! there are two cutting teeth, on the right and
the left side, which are implanted in a bone
| which corresponds to this, and is called the
| intermediary. The eye-teeth and grinders
| are implanted i'll another bone, which is called
| the upper maXillary and the intermediary
and upper maXillary together, in one arch,
form the margin of the mouth. Now in the
| perch 1t is very different. We have one bone
which extends in this way from the anterior
| part OF the mouth to the end of the cleft and
that one bone is provided with teeth along its
| margin, and forms alone the upper margin of
| the mouth while another bone. placed he
| hind, and forming in no way part of tbe
mouth, sustaining no teeth Whatever renre-
! sents the upper maNillary. 1t is the anterior
which TAnIaglnts fl., s,,A.