Dermopteres. FISHES. Amphyoxids. 109 
or mere albuminous concretions, wanting the structure 
of cartilage or of bone. They have no air-bladder, 
and no pancreatic apparatus to assist in digestion. 
Their jaws also differ from those of other fishes, having 
more the character of pharyngeal arches than of maxil- 
laries and mandibles. They are divided by Professor 
Owen into two sub-orders : I. the Pharyngobranchs or 
Cirrhostomes, of which the Lancelets are the only 
representatives ; and II. the Marsipohranchs or Cyclos- 
tomes, embracing the families of the Myxinoids or 
Hags and the Petromyzontids or Lampreys. 
Family L— AMPHYOXIDS. 
THE lANCElET {AmpMoxus lanceolatus or Brancli- 
iostoma luh'icum) was first detected on the Cornish 
coast, and a specimen being sent to Pallas, lire cele- 
brated naturalist of Russia, was described by him as a 
slug. The Cornish ichthyologist, Jonathan Couch, 
Esq., of Polperro, rediscovered it in 1 831 on the same 
coast where it was first found, and many examples have 
since been obtained on the English, Scottish, Irish, 
Norwegian, Mediterranean, and West Indian coasts, 
principally by dredging in water of various depths down 
to fifty fathoms. The same, or a closely resembling 
species, has been brought from China, so that this 
embryonic type of a vertebral is wide’y diffused in the 
ocean. 
One is not surprised that when modern zoology was 
in its infancy, this curious creature was taken for a 
mollusc, and that it was left for the late Mr. Yarrell 
to detect the nervous axis and establish its piscine 
character, since it has no head, being as its generic 
name imparts sharp at both ends, no gills, no heart, no 
stomach distinct from the small gut, and no other fins 
than a narrow border of skin above and below. It is 
a thin, transparent animal, destitute of that swelling of 
the proximal end of the spinal marrow (or myelon) 
which is called the brain. As the brain of fishes, 
though composed of several pairs of tubercles of ner- 
vous substance, and of some single mesial ones, is 
small in comparison of the cranial cavity in which it is 
lodged, it is to the absence of the skull, the jaws, the 
hyoid apparatus, and the other parts connected there- 
with, that the sharpness of the proximal end of the 
Lancelot is to be attributed. The vertebral chord con- 
sists of a series of discoid cells closely pressed together 
in a fibrous sheath, whose upper layers separate and 
form a tube for lodging the myelon ; and in like manner 
the lower layers of the sheath form behind the vent a 
haemal canal, no cartilaginous deposits being traceable 
in either. Very simple is the neural axis itself, as it 
exhibits none of the fibrous or tubular structure which 
exists in the brain and myelon of the higher vertebrals, 
but is composed solely of isolated cells, forming a ner- 
vous tract, which is riband -shaped in the middle third, 
and a little more round towards the ends. In its course 
it gives off about sixty pairs of nerves, which spring 
from single roots. 
The entire nervous system of the Lancelet is so 
simple, that Professor Owen considers it to be typified 
bj’’ that of the entozoons or intestinal worms. The 
eye is a mere speck, which some able anatomists have 
failed to detect; and as it is not furnished with muscles 
for motion, vision can scarcely extend beyond the mere 
perception of light. The animal, however, is very 
active, and when disturbed speedily hides itself among 
sand or gravel. 
The length of this fish is generally under two inches; 
and its longitudinal mouth, situated under the proximal 
acute extremity, is fringed by feelers supported by the 
only parts of the skeleton that have the consistence of 
cartilage. The cavit}' of the mouth and the commence- 
ment of the digestive canal are of great comparative 
dimensions, since they make up half the bulk and length 
of the fish. The pharynx is a kind of barrel-shaped 
cage, with more than a hundred vertical slits beset 
with vibratile cilise, and opening into the cavity of the 
abdomen in which the cage is suspended. A great 
dorsal and ventral blood-vessel encircles the interior 
of the animal longitudinally, and sends numerous 
branches to the pharyngeal cage, which thus serves 
both for the passage of the aliment, and for the oxy- 
genation of the blood, through exposure to the air 
contained in the water that flows through it. The 
alimentary particles pass into a simple intestinal canal 
issuing from the distal end of the pharyngeal cage near 
its dorsal aspect; and the w'ater of respiration escaping 
through the lateral ciliated slits into the cavity of the 
belly, finally issues by an external ventral opening 
situated between the intestinal vent and the mouth. 
Through this single ventral gill-opening the eggs of the 
animal are also extruded. In animals low in the scale, 
we find a single viscus performing two or more func- 
tions for which special organs are assigned in animals 
of a higher order. Duges ascertained that during the 
first hour of a tadpole’s existence, the blood is aerated 
solely through the medium of the skin, and that a 
special organ of respiration is not developed until the 
second or third hour after the animal has made its 
escape from the egg. Moreover, in several osseous 
fishes the digestive canal acts an auxiliaiy part in the 
oxygenation of the blood. The misgurn loach (cohitis 
fossilis), for instance, sw'allows atmospheric air by the 
mouth, and discharges azote through the vent after the 
oxygen has been consumed in its passage through the 
intestinal tube, while the gills at the same time exhale 
much carbonic acid.* Except that it is not aided by 
gills, the greatly developed pharynx of the Lancelet 
has a similar function. Owen, however, considers 
some fringe-like processes of membrane which float 
in the cavity of the mouth of the Lancelet to be “ free 
inoperculate gills.” 
Family II.— MYXINOIDS.-(Plate I, fig. 1.) 
The term Marsipobranch applied to the second sub- 
order of Dermopteres, means “gills in pouches;” wdiile 
the other appellation of Cyclostome used by Cuvier, 
has reference to the circular suctorial mouths which 
all the adult members of the group possess, and which 
is in fact an essential part of their structure, since all 
these fishes after passing their larval stage are parasites, 
and live by sucking in the fluid and soft parts of the 
* Bischoff ; Baumert, &c., quoted by Milne-Edwards, Phys. 
