THE APODES, OR EEL-LIKE FISHES
=THE Eels.=—We may here break the sequence from the _Isospondyli_ to the
other soft-rayed fishes, to interpolate a large group of uncertain
origin, the series or subclass of eels.
The mass of apodal or eel-like fishes has been usually regarded as
constituting a single order, the Apodes (ἄ, without; ποῦς, foot). The
group as a whole is characterized by the almost universal separation of
the shoulder-girdle from the skull, by the absence of the mesocoracoid
arch on the shoulder-girdle, by the presence of more than five pectoral
actinosts, as in the Ganoid fishes, by the presence of great numbers of
undifferentiated vertebræ, giving the body a snake-like form, by the
absence in all living forms of the ventral fins, and, in all living
forms, by the absence of a separate caudal fin. These structures
indicate a low organization. Some of them are certainly results of
degeneration, and others are perhaps indications of primitive
simplicity. Within the limits of the group are seen other features of
degeneration, notably shown in the progressive loss of the bones of the
upper jaw and the membrane-bones of the head and the degradation of the
various fins. The symplectic bone is wanting, the notochord is more or
less persistent, the vertebral centra always complete constricted
cylinders, none coalesced. But, notwithstanding great differences in
these regards, the forms have been usually left in a single order, the
more degraded forms being regarded as descended from the types which
approach nearest to the ordinary fishes. From this view Professor Cope
dissents. He recognizes several orders of eels, claiming that we should
not unite all these various fishes into a single order on account of the
eel-like form. If we do so, we should place in another order those with
the fish-like form. It is probable, though not absolutely certain, that
the _Apodes_ are related to each other. The loss among them, first, of
the connection of the post-temporal with the skull; second, of the
separate caudal fin and its hypural support; third, of the distinct
maxillary and premaxillary; and fourth, of the pectoral fins, must be
regarded as successive phases of a general line of degradation. The
large number of actinosts, the persistence of the notochord, the absence
of spines, and the large numbers of vertebræ seem to be traits of
primitive simplicity. Special lines of degeneration are further shown by
deep-sea forms. What the origin of the _Apodes_ may have been is not
known with any certainty. They are soft-rayed fishes, with the
air-bladder connected by a tube with the œsophagus, and with the
anterior vertebræ not modified. In so far they agree with the
_Isospondyli_. In some other respects they resemble the lower
_Ostariophysi_, especially the electric eel and the eel-like catfishes.
But these resemblances, mainly superficial, may be wholly deceptive; we
have no links which certainly connect the most fish-like Apodes with any
of the other orders. Probably Woodward's suggestion that they may form a
series parallel with the _Isospondyli_ and independently descended from
Tertiary Ganoids deserves serious consideration. Perhaps the most
satisfactory arrangement of these fishes will be to regard them as
constituting four distinct orders for which we may use the names
_Symbranchia_ (including _Ichthyocephali_ and _Holostomi_), _Apodes_
(including _Enchelycephali_ and _Colocephali_), _Carencheli_, and
_Lyomeri_.
=Order Symbranchia.=—The _Symbranchia_ are distinguished by the
development of the ordinary fish mouth, the maxillary and premaxillary
being well developed. The gill-openings are very small, and usually
confluent below. These fresh-water forms of the tropics, however
eel-like in form, may have no real affinity with the true eels. In any
event, they should not be placed in the same order with the latter.
The eels of the suborder _Ichthyocephali_ (ιχθύς, fish; κεφαλή, head)
have the head distinctly fish-like. The maxillary, premaxillary, and
palatines are well developed, and the shoulder-girdle is joined by a
post-temporal to the skull. The body is distinctly eel-like, the tail
being very short and the fins inconspicuous. The number of vertebræ is
unusually large. The order contains the single family _Monopteridæ_, the
rice-field eels, one species, _Monopterus albus_, being excessively
common in pools and ditches from China and southern Japan to India.
The eels of the suborder _Holostomi_ (ὀλός, complete; στόμα, mouth)
differ from these mainly in the separation of the shoulder-girdle from
the skull, a step in the direction of the true eels. The _Symbranchidæ_
are very close to the _Monopteridæ_ in external appearance, small,
dusky, eel-like inhabitants of sluggish ponds and rivers of tropical
America and the East Indies. The gill-openings are confluent under the
throat. _Symbranchus marmoratus_ ranges northward as far as Vera Cruz,
having much the habit of the rice-field eel of Japan and China. The
_Amphipnoidæ_, with peculiar respiratory structures, abound in India.
_Amphipnous cuchia_, according to Günther, has but three gill-arches,
with rudimentary lamina and very narrow slits. To supplement this
insufficient branchial apparatus, a lung-like sac is developed on each
side of the body behind the head, opening between the hyoid and the
first branchial arch. The interior of the sac is abundantly provided
with blood-vessels, the arterial coming from the branchial arch, whilst
those issuing from it unite to form the aorta. _Amphipnous_ has
rudimentary scales. The other _Holostomi_ and _Ichthyocephali_ are naked
and all lack the pectoral fin.
The _Chilobranchidæ_ are small sea-fishes from Australia, with the tail
longer than the rest of the body, instead of much shorter as in the
others.
No forms allied to _Symbranchus_ or _Monopterus_ are recorded as
fossils.
=Order Apodes, or True Eels.=—In this group the shoulder-girdle is free
from the skull, and the bones of the jaws are reduced in number, through
coalescence of the parts.
Three well-marked suborders may be recognized, groups perhaps worthy of
still higher rank: _Archencheli_, _Enchelycephali_, and _Colocephali_.
=Suborder Archencheli.=—The _Archencheli_, now entirely extinct, are
apparently the parents of the eels, having, however, certain traits
characteristic of the _Isospondyli_. They retain the separate caudal
fin, with the ordinary hypural plate, and Professor Hay has recently
found, in an example from the Cretaceous of Mount Lebanon, remains of
distinct ventral fins. These traits seem to indicate an almost perfect
transition from the _Isospondyli_ to the _Archencheli_.
One family may be recognized at present, _Urenchelyidæ_.
The earliest known eel, _Urenchelys avus_, occurs in the upper
Cretaceous at Mount Lebanon. It represents the family _Urenchelyidæ_,
apparently allied to the _Anguillidæ_, but having a separate caudal fin.
Its teeth are small, conical, blunt, in many series. There are more than
100 vertebræ, the last expanded in a hypural. Pectorals present. Scales
rudimentary; dorsal arising at the occiput. Branchiostegals slender, not
curved around the opercle. _Urenchelys anglicus_ is another species,
found in the chalk of England.
=Suborder Enchelycephali.=—The suborder _Enchelycephali_ (ἔγχελυς, eel;
κεφαλή, head) contains the typical eels, in which the shoulder-girdle is
free from the skull, the palatopterygoid arch relatively complete, the
premaxillaries wanting or rudimentary, the ethmoid and vomer coalesced,
forming the front of the upper jaw, the maxillaries lateral, and the
cranium with a single condyle. In most of the species pectoral fins are
present, and the cranium lacks the combined degradation and
specialization shown by the morays (_Colocephali_).
=Family Anguillidæ.=—The most primitive existing family is that of the
typical eels, _Anguillidæ_, which have rudimentary scales oblong in
form, and set separately in groups at right angles with one another.
These fishes are found in the fresh and brackish waters of all parts of
the world, excepting the Pacific coast of North America and the islands
of the Pacific. In the upper Great Lakes and the upper Mississippi they
are also absent unless introduced. The species usually spawn in the sea
and ascend the rivers to feed. But some individuals certainly spawn in
fresh water, and none go far into the sea, or where the water is
entirely salt. The young eels sometimes ascend the brooks near the sea
in incredible numbers, constituting what is known in England as
"eel-fairs." They will pass through wet grass to surmount ordinary
obstacles. Niagara Falls they cannot pass, and according to Professor
Baird "in the spring and summer the visitor who enters under the sheet
of water at the foot of the falls will be astonished at the enormous
numbers of young eels crawling over the slippery rocks and squirming in
the seething whirlpools. An estimate of hundreds of wagon-loads, as seen
in the course of the perilous journey referred to, would hardly be
considered excessive by those who have visited the spot at a suitable
season of the year." "At other times large eels may be seen on their way
down-stream, although naturally they are not as conspicuous then as are
the hosts of the young on their way upstream. Nevertheless it is now a
well-assured fact that the eels are catadromous, that is, that the old
descend the watercourses to the salt water to spawn, and the young, at
least of the female sex, ascend them to enjoy life in the fresh water."
[Illustration:
FIG. 101.—Common Eel, _Anguilla chrisypa_ Rafinesque. Holyoke, Mass.
]
=Reproduction of the Eel.=—Dr. Gill ("Riverside Natural History," p.
103) gives the following account of the reproduction of _Anguilla_:
"The generation of the eel was long involved in great mystery, and the
knowledge thereof is one of the recent acquisitions of scientific
investigation. So late, indeed, as 1880 it was declared that 'their mode
of propagation is still unknown.' In want of positive knowledge the rein
has been given to loose hypothesis and conjecture. It has been variously
asserted that eels were generated from slime, from dew, and from the
skins of old eels or of snakes. The statement that they come from
horse-hairs is familiar to many country boys, and the origin of this
belief is due simply to the fact that there are certain aquatic worms,
known under the generic name _Gordius_, which are elongated and
apparently smooth like the eel, and which may be found in the same
waters. It was one of the ideas of the Greek to attribute their
paternity, as of many other doubtful offspring, to the convenient
Jupiter. The statement that they are viviparous has arisen from two
causes: one the existence of intestinal worms, and the other from the
confusion of the eel with an elongated and consequently eel-like but
otherwise very different form, the _Zoarces viviparus_. The _Zoarces_ is
indeed, in Germany as well as in the Scandinavian countries, generally
known as the Aal-mutter, or eel-mother, and thus in its name perpetuates
the fancy. Even where eels are to be found in extreme abundance, and
where they are the objects of a special culture, like erroneous opinions
prevail. Thus, according to Jacoby, about the lagoon of Comacchio there
is an 'ineradicable belief among the fishermen that the eel is born of
other fishes; they point to special differences in color and especially
in the common mullet, _Mugil cephalus_, as the causes of variation in
color and form among eels. It is a very ancient belief, widely prevalent
to the present day, that eels pair with water-snakes. In Sardinia the
fishermen cling to the belief that a certain beetle, the so-called
water-beetle, _Dytiscus ræselii_, is the progenitor of eels, and they
therefore call this "mother of eels."' The assignment of such maternity
to the water-beetle is doubtless due to the detection of the hair-worm,
or Gordius, in the insect by sharp-sighted but unscientific observers,
and, inasmuch as the beetle inhabits the same waters as the eel, a very
illogical deduction has led to connect the two together.
"All such beliefs as have been thus recounted are due to the
inconspicuous nature of the generative organs in eels found in fresh
waters and at most seasons—a characteristic which is in strong contrast
to the development of corresponding parts in fishes generally.
Nevertheless the ovaries of the eel were discovered, as long ago as
1707, by Dr. Sancassini of Comacchio, and described by the celebrated
Valisneri (after whom the plant _Valisneria_ was named) in 1710, again
by Mondini in 1777, and almost contemporaneously by O. J. Müller of
Denmark. Later the illustrious Rathke (in 1824, 1838, and 1850) and also
Hornbaum-Hornschuch published the results of special investigations, and
figured the eggs. But it was only in 1873 (after several futile
endeavors by others) that the male organ of the eel was recognized, also
by an Italian naturalist, Dr. Syrski, in small individuals of the
species, and a previous idea that the eel was hermaphroditic thereby
dispelled. The sexual differences are correlated with external ones, and
generally the males and females, when adult, can be told apart. Jacoby
testifies that he examined large numbers with a view to solve this
question. The most important differences relate to (1) size; (2) form of
the snout; (3) color; (4) dorsal fin; and (5) size of the eyes. (1) The
males rarely attain a length of more than seventeen to nineteen inches,
while adult females are generally much larger; (2) the snout in the male
is attenuated and rather pointed, while in the female it is
comparatively broad and blunt; (3) the male is of a deep darkish green,
or often a deep black with a shining luster and a whitish belly, while
the female has a clearer color, usually of a greenish hue on the back
and yellowish on the belly; (4) the dorsal fin is lower and less
developed in the male than in the female; and (5) the eye of the male is
large and that of the female, as a rule, comparatively small. These
characters, however, do not always hold good. Jacoby remarked that
'special reference having been paid to the height and narrowness of the
dorsal fin, much success has been met with in picking out, in the
fish-market of Trieste, the eels which possessed the organ of Syrski
(that is, the male organ); absolute certainty, however, in recognizing
them cannot be guaranteed. If one is searching among living eels with no
characters in mind,—with the exception of the first, that of length,—he
will find in every ten eels, on an average, eight females and two with
the supposed male organ; but if the selection is made with a careful
reference to all these marks of difference, the proportion changes, and
out of every ten examples about eight will be found with the supposed
male organ.'
"According to Herr Benecke, 'it may be assumed with the greatest safety
that the eel lays its eggs like most other fish, and that, like the
lamprey, it spawns only once and then dies. All the eggs of a female
show the same degree of maturity, while in the fish which spawn every
year, besides the large eggs which are ready to be deposited at the next
spawning period, there exist very many of much smaller size, which are
destined to mature hereafter and be deposited in other years. It is very
hard to understand how young eels could find room in the body of their
mother if they were retained until they had gained any considerable
size. The eel embryo can live and grow for a long time supported by the
little yolk, but, when this is done, it can only obtain food outside of
the body of its mother. The following circumstances lead us to believe
that the spawning of the eel takes place only in the sea: (1) that the
male eel is found only in the sea or brackish water, while female eels
yearly undertake a pilgrimage from the inland waters to the sea, a
circumstance which has been known since the time of Aristotle, and upon
the knowledge of which the principal capture of eels by the use of fixed
apparatus is dependent; (2) that the young eels, with the greatest
regularity, ascend from the sea into the rivers and lakes.'"
All statements in opposition to this theory are untenable, since the
young eels never find their way into landlocked ponds in the course of
their wanderings, while eels planted in such isolated bodies of water
thrive and grow rapidly, but never increase in numbers. Another still
more convincing argument is the fact that in lakes which formerly
contained many eels, but which, by the erection of impassable weirs,
have been cut off from the sea, the supply of eels has diminished, and
after a time only scattering individuals, old and of great size, are
taken in them. An instance of this sort occurred in Lake Muskengorf in
West Prussia. If an instance of the reproduction of the eel in fresh
water could be found, such occurrences as these would be quite
inexplicable.
In the upper stretches of long rivers the migration of the eels begins
in April or in May; in their lower stretches and shorter streams, later
in the season. In all running waters the eel-fishery depends upon the
downward migrations; the eels press up the streams with occasional
halts, remaining here and there for short periods, but always make their
way above. They appear to make the most progress during dark nights,
when the water is troubled and stormy, for at this time they are
captured in the greatest numbers. It is probable that after the eels
have once returned to the sea and there deposited their spawn, they
never can return into fresh water, but remain there to die. A great
migration of grown eels in spring or summer has never been reported, and
it appears certain that all the female eels which have once found their
way to the sea are lost to the fisherman.
=Food of the Eel.=—Eels, in the words of Mr. W. H. Ballou, are "among
the most voracious of carnivorous fishes. They eat most inland fishes,
except the garfish and the chub. Investigation of six hundred stomachs
by Oswego fishermen showed that the latter bony fish never had a place
in their bill of fare. They are particularly fond of game-fishes, and
show the delicate taste of a connoisseur in their selection from choice
trout, bass, pickerel, and shad. They fear not to attack any object when
disposed, and their bite in human flesh shows even a vicious attitude
towards man. On their hunting excursions they overturn huge and small
stones alike, working for hours if necessary, beneath which they find
species of shrimp and crayfish, of which they are exceedingly fond. Of
shrimps they devour vast numbers. Their noses are poked into every
imaginable hole in their search for food, to the terror of innumerable
small fishes."
In the opinion of Mr. Ballou, too, "eels are to the water what the
fishhawk is to the air. They are, perhaps, the most powerful and rapid
of natatorians. Again, they hide in the mud beneath some log or
overhanging rock, and dart out with tremendous fury at the unsuspecting
prey. They attack the spawn of other fishes open-mouthed, and are even
said to suck the eggs from an impaled female. They fearlessly and
rapidly dive head-foremost in the mud, disappearing from view in the
twinkling of a star. They are owl-like in their habits, committing many
of their depredations at night.
"No fish is yet reported to utilize a full-grown eel as food. Pickerel,
garfish, and bass, which are particularly numerous in these lakes, are
supposed to literally devour the young fry. Mr. Sawyer describes the
operation of the pickerel darting through a long column of young eels
open-mouthed and devouring vast numbers of them."
=Larva of the Eel.=—The translucent band-shaped larva of the common eel
has been very recently identified and described by Dr. Eigenmann. It is
probable that all true eels, _Enchelycephali_, pass through a
band-shaped or leptocephalous stage, as is the case with _Albula_ and
other _Isospondyli_. In the continued growth the body becomes firmer,
and at the same time much shorter and thicker, gradually assuming the
normal form of the species in question.
[Illustration:
FIG. 102.—Larva of Common Eel, _Anguilla chrisypa_ (Rafinesque),
called _Leptocephalus grassii_. (After Eigenmann.)
]
In a recent paper Dr. Carl H. Eigenmann has very fully reviewed the
life-history of the eel. The common species live in fresh waters,
migrating to the sea in the winter. They deposit in deep water minute
eggs that float at the surface. The next year they develop into the
band-shaped larva. The young eels enter the streams two years after
their parents drop down to the sea. It is doubtful whether eels breed in
fresh water. The male eel is much smaller than the female.
The eel is an excellent food-fish, the flesh being tender and oily, of
agreeable flavor, better than that of any of its relatives. Eels often
reach a large size, old individuals of five or six feet in length being
sometimes taken.
=Species of Eels.=—The different species are very closely related. Not
more than four or five of them are sharply defined, and these mostly in
the South Seas and in the East Indies. The three abundant species of the
north temperate zone, _Anguilla anguilla_ of Europe, _Anguilla chrisypa_
of the eastern United States, and _Anguilla japonica_ of Japan, are
scarcely distinguishable. In color, size, form, and value as food they
are all alike.
Fossil species referred to the _Anguillidæ_ are known from the early
Tertiary. _Anguilla leptoptera_ occurs in the Eocene of Monte Bolea, and
_Anguilla elegans_ in the Miocene of Œningen in Baden. Other fossil eels
seem to belong to the _Nettastomidæ_ and _Myridæ_.
=Pug-nosed Eels.=—Allied to the true eel is the pug-nosed eel,
_Simenchelys parasiticus_, constituting the family of _Simenchelyidæ_.
This species is scaled like a true eel, has a short, blunt nose, and
burrows its way into the bodies of halibut and other large fishes. It
has been found in Newfoundland and Madeira. Another family possessing
rudimentary scales is that of the _Synaphobranchidæ_, slender eels of
the ocean depths, widely distributed. In these forms the gill-openings
are confluent. _Synaphobranchus pinnatus_ is the best-known species.
[Illustration:
FIG. 103.—Pug-nosed Eel, _Simenchelys parasiticus_ Gill. Sable Island
Bank.
]
[Illustration:
FIG. 104.—_Synaphobranchus pinnatus_ (Gronow). Le Have Bank.
]
=Conger-eels.=—The _Leptocephalidæ_, or conger-eels, are very similar to
the fresh-water eels, but are without scales and with a somewhat
different mouth, the dorsal beginning nearer to the head.
The principal genus is _Leptocephalus_, including the common conger-eel
(_Leptocephalus conger_) of eastern America and Europe and numerous very
similar species in the tropics of both continents. These fishes are
strictly marine and, reaching the length of five or six feet, are much
valued as food. The eggs are much larger than those of the eel and are
produced in great numbers, so that the female almost bursts with their
numbers. Dr. Hermes calculated that 3,300,000 were laid by one female in
an aquarium.
These eggs hatch out into transparent band-like larva, with very small
heads formerly known as _Leptocephalus_, an ancient name which is now
taken for the genus of congers, having been first used for the larva of
the common conger-eel. The loose watery tissues of these "ghost-fishes"
grow more and more compact and they are finally transformed into young
congers.
[Illustration:
FIG. 105.—Conger-eel, _Leptocephalus conger_ (L.). Noank, Conn.
]
The _Murænesocidæ_ are large eels remarkable for their strong knife-like
teeth. _Murænesox savanna_ occurs in the West Indies and in the
Mediterranean, _Murænesox cinereus_ in Japan, and _Murænesox coniceps_
on the west coast of Mexico, all large and fierce, with teeth like
shears. The _Myridæ_ are small and worm-like eels closely allied to the
congers, having the tail surrounded by a fin, but the nostrils labial.
_Myrus myrus_ is found in the Mediterranean. Species of _Eomyrus_,
_Rhynchorhinus_, and _Paranguilla_ apparently allied to _Myrus_ occur in
the Eocene. Other related families, mostly rare or living in the deep
seas, are the _Ilyophidæ_, _Heterocongridæ_, and _Dysommidæ_.
[Illustration:
FIG. 106.—Larva of Conger-eel (_Leptocephalus conger_), called
_Leptocephalus morrissi_. (After Eigenmann.)
]
=The Snake-eels.=—Most varied of the families of eels is the
_Ophichthyidæ_, snake-like eels recognizable by the form of the tail,
which protrudes beyond the fins. Of the many genera found in tropical
waters several are remarkable for the sharply defined coloration,
suggesting that of the snake. Characteristic species are _Chlevastes
colubrinus_ and _Leiuranus semicinctus_, two beautifully banded species
of Polynesia, living in the same holes in the reefs and colored in the
same fashion. Another is _Callechelys melanotænia_. The commonest
species on the Atlantic coast is the plainly colored _Ophichthus
gomesi_.
[Illustration:
FIG 107.—_Xyrias revulsus_ Jordan & Snyder. Family _Ophichthyidæ_.
Misaki, Japan.
]
In the genus _Sphagebranchus_, very slender eels of the reefs, the fins
are almost wanting.
[Illustration:
FIG. 108.—_Myrichthys pantostigmius_ Jordan & McGregor. Clarion
Island.
]
[Illustration:
FIG. 109.—_Ophichthus ocellatus_ (Le Sueur). Pensacola.
]
Allied to the Congers is the small family of duck-billed eels
(_Nettastomidæ_) inhabiting moderate depths of the sea. _Nettastoma
bolcense_ occurs in the Eocene of Monte Bolca. The produced snout forms
a transition to the really extraordinary type of thread-eels or
snipe-eels (_Nemichthyidæ_), of which numerous genera and species live
in the oceanic depths. In _Nemichthys_ the long, very slender,
needle-like jaws are each curved backward so that the mouth cannot by
any possibility be shut. The body is excessively slender and the fish
swims with swift undulations, often near the surface, and when seen is
usually taken for a snake. The best-known species is _Nemichthys
scolopaceus_ of the Atlantic and Pacific. _Nemichthys avocetta_, very
much like it, has been twice taken in Puget Sound.
[Illustration:
FIG. 110.—Thread-eel, _Nemichthys avocetta_ Jordan & Gilbert.
Vancouver Island.
]
=Suborder Colocephali, or Morays.=—In the suborder _Colocephali_ (κολός,
deficient; κεφαλή, head) the palatopterygoid arch and the membrane-bones
generally are very rudimentary. The skull is thus very narrow, the
gill-structures are not well developed, and in the chief family there
are no pectoral fins. This group is very closely related to the
_Enchelycephali_, from which it is probably derived.
[Illustration:
FIG. 111.—Jaws of _Nemichthys avocetta_ Jordan & Gilbert.
]
In the great family of morays (_Murænidæ_) the teeth are often very
highly developed. The muscles are always very strong and the spines bite
savagely, a live moray being often able to drive men out of a boat. The
skin is thick and leathery, and the coloration is highly specialized,
the pattern of color being often elaborate and brilliant. In _Echidna
zebra_ for example the body is wine-brown, with cross-stripes of golden
yellow. In _Muræna_ each nostril has a barbel. _Muræna helena_, the
oldest moray known, is found in Europe. In _Gymnothorax_, the largest
genus, only the anterior nostrils are thus provided. _Gymnothorax
mordax_ of California is a large food-fish, as are also the brown
_Gymnothorax funebris_ and the spotted _Gymnothorax moringa_ in the West
Indies. These and many other species may coil themselves in crevices in
the reefs, whence they strike out at their prey like snakes, taking
perhaps the head of a duck or the finger of a man.
In many of the morays the jaws are so curved and the mouth so filled
with knife-like teeth that the jaws cannot be closed. This fact,
however, renders no assistance to their prey, as the teeth are adapted
for holding as well as for cutting.
In _Enchelynassa bleekeri_, a huge wine-colored eel of the South Seas,
the teeth are larger than in any other species. _Evenchelys_
(_macrurus_) is remarkable for its extraordinary length of tail,
_Echidna_ for its blunt teeth, and _Scuticaria_, _Uropterygius_, and
_Channomuræna_ for the almost complete absence of fins. In _Anarchias_
(_allardicei_; _knighti_), the anal fin is absent. The flesh of the
morays is rather agreeable in taste, but usually oily and not readily
digestible, less wholesome than that of the true eels.
[Illustration:
FIG. 112.—_Muræna retifera_ Garman. Charleston, S. C.
]
The _Myrocongridæ_ are small morays with developed pectoral fins. The
species are few and little known.
=Family Moringuidæ.=—Structurally one of the most peculiar of the groups
of eels is the small family of _Moringuidæ_ of the East and West Indies.
In these very slender, almost worm-like fishes the heart is placed very
far behind the gills and the tail is very short. The fins are very
little developed, and some forms, as _Gordiichthys irretitus_ of the
Gulf of Mexico, the body as slender as a whiplash, possess a very great
number of vertebræ. _Moringua hawaiiensis_ occurs in Hawaii, _M.
edwardsi_ in the Bahamas. This family probably belongs with the morays
to the group of _Colocephali_, although its real relationships are not
wholly certain.
=Order Carencheli, the Long-necked Eels.=—Certain offshoots from the
Apodes so widely diverging in structure that they must apparently be
considered as distinct orders occur sparingly in the deep seas. One of
these, _Derichthys serpentinus_, the long-necked eel, constitutes the
sole known species of the suborder _Carencheli_ (καρά, head; ἔγχελυς,
eel). In this group the premaxillaries and maxillaries are present as in
ordinary fishes, but united by suture and soldered to the cranium. As in
true eels, the shoulder-girdle is remote from the skull. The head is set
on a snake-like neck. The single species representing the family
_Derichthyidæ_ was found in the abysmal depths of the Gulf Stream.
[Illustration:
FIG. 113.—_Gymnothorax berndti_ Snyder. Hawaii. Family _Murænidæ_.
]
[Illustration:
FIG. 114.—_Gymnothorax jordani_ (Evermann & Marsh). Family _Murænidæ_.
Puerto Rico.
]
[Illustration:
FIG. 115.—Moray, _Gymnothorax moringa_ Bloch. Family _Murænidæ_.
Tortugas.
]
[Illustration:
FIG. 116.—_Derichthys serpentinus_ Gill. Gulf Stream.
]
[Illustration:
FIG. 117.—Gulper-eel, _Gastrostomus bairdi_ Gill & Ryder. Gulf Stream.
]
=Order Lyomeri, or Gulpers.=—Still more aberrent and in many respects
extraordinary are the eels of the order or suborder _Lyomeri_ (λυός,
loose; μέρος, part), known as "Gulpers." These are degenerate forms,
possibly degraded from some conger-like type, but characterized by an
extreme looseness of structure unique among fishes. The gill-arches are
reduced to five small bars of bone, not attached to the skull, the
palatopterygoid arch is wholly wanting, the premaxillaries are wanting,
as in all true eels, and the maxillaries loosely joined to the skull.
The symplectic bone is wanting, and the lower jaw is so hinged to the
skull that it swings freely in various directions. In place of the
lateral line are singular appendages. Dr. Gill says of these fishes:
"The entire organization is peculiar to the extent of anomaly, and our
old conceptions of the characteristics of a fish require to be modified
in the light of our knowledge of such strange beings." Special features
are the extraordinary size of the mouth, which has a cavity larger than
that of the rest of the body, the insertion of the very small eye at the
tip of the snout, and the relative length of the tail. The whole
substance is excessively fragile as usual with animals living in great
depths and the color is jet black. Three species have been described,
and these have been placed in two families, _Saccopharyngidæ_, with the
trunk (gill-opening to the vent) much longer than the head, and
_Eurypharyngidæ_, with the trunk very short, much shorter than the head.
The best-known species is the pelican eel (_Eurypharynx pelacanoides_),
of the coast of Morocco, described by Vaillant in 1882. _Gastrostomus
bairdi_, very much like it, occurs in the great depths under the Gulf
Stream. So fragile and so easily distorted are these fishes that it is
possible that all three are really the same species, for which the
oldest name would be _Saccopharynx ampullaceus_. Of this form four
specimens have been taken in the Atlantic, one of them six feet long,
carried to the surface through having swallowed fishes too large to be
controlled. To be carried above its depth in a struggle with its prey is
one of the greatest dangers to which the abysmal fishes are subject.
=Order Heteromi.=—The order of _Heteromi_ (ἑτερός, different; ὤμος,
shoulder), or spiny eels, may be here noticed for want of a better
place, as its affinities are very uncertain. Some writers have regarded
it as allied to the eels; some have placed it among the Ganoids. Others
have found affinities with the sticklebacks, and still others with the
singular fresh-water fishes called _Mastacembelus_. The _Heteromi_ agree
with the eels, as well as with _Mastacembelus_, in having the scapular
arch separate from the cranium. Unlike all the true eels, most of the
species have true dorsal and anal spines, as in the _Percesoces_ and
_Hemibranchii_. The ventral fins, when present, are abdominal and each
with several spines in front, a character not found among the
_Acanthopteri_. There is no mesocoracoid.
The air-bladder has a duct, and the coracoids, much as in the _Xenomi_,
are reduced to a single lamellar imperforate plate. The two groups have
little else in common, however, and this trait is possibly primitive in
both cases, more likely to have arisen through independent degeneration.
The separation of the shoulder-girdle doubtless indicates no affinity
with the eels, as the bones of the jaws are quite normal. Two families
are known, both from the deep sea, besides an extinct family in which
spines are not developed.
The _Notacanthidæ_ are elongate, compressed, ending in a band-shaped,
tapering tail; the back has numerous free spines and few or no soft
rays, and the mouth is normal, provided with teeth. The species of
_Notacanthus_ are few and scantily preserved. Those of _Macdonaldia_ are
more abundant. _Macdonaldia challengeri_ is from the North Pacific,
being once taken off Tokio. The extinct family of _Protonotacanthidæ_
differs in the total absence of dorsal spines and fin-rays; the single
species, _Pronotocanthus sahel-almæ_, originally described as a
primitive eel, occurs in the Cretaceous of Mount Lebanon.
The _Lipogenyidæ_ have a round, sucker-like mouth, with imperfect lower
jaw, but are otherwise similar. _Lipogenys gilli_ was dredged in the
Gulf Stream.
[Illustration:
FIG. 118.—_Notacanthus phasganorus_ Goode & Bean. Grand Banks.
]
Dr. Boulenger has recently extended the group of _Heteromi_ by the
addition of the _Dercetidæ_, _Halosauridæ_ (_Lyopomi_), and the
_Fierasferidæ_. We can hardly suppose that all these forms are really
allied to _Notacanthus_.