142 
Mai,acopterous Apodals. FISHES. Gysinotids. 
down b}' mucus. In tlie woodcut it is shown partially 
disengaged. 
Professor Hyrtl has shown that Gymnarchus resem- 
bles Mormyrus in possessing a side-chamber in the 
bulb of the gill-artery ; it has moreover a serpentiform 
complication of the air-bladder. 
Gymnotus is the only genus of the family which is 
scaleless, and it is furnished with a powerful galvanic 
apparatus, an organ not hitherto found in scaly fishes. 
In the Gymnotus, or Electric Eel, the galvanic organ 
occupies about half the thickness of the tail, and is 
divisible into four longitudinal bundles ; a thicker 
Siiarp-nosed Thong-fish (Steruarchus o.xyrhinchns). 
Fig. 36. 
upper pair and a slender lower pair laid along the base 
of the anal fin. Each bundle is constructed of parallel 
membranes and horizontal discs, close to each other, 
including multitudes of transverse prismatic cells filled 
with gelatinous matter, and largely supplied with nervous 
filaments. Humboldt’s description of the way in which 
the Gymnotes use their batteries is highl}' interesting. 
These fish abound, he says, in the vicinity of Cala- 
boza in South America, and the Indians well aware of 
the danger of encountering them when their powers 
are in vigour, collect from twenty to thirty horses, drive 
them into the pools, and when the Gymnotes have 
exhausted their electric batteries on the poor horses, 
they can he taken without risk. Time and repose are 
needed before the batteries are ready to act again. 
The horses at first exhibit much agitation and terror, 
but are prevented from leaving the ponds by an encir- 
cling band of Indians who strike them with bamboos. 
“The eels,” says Humboldt, “stunned and confused by 
the rush of the horses, defended themselves by reite- 
rated electric discharges, and for some time seemed 
likely to gain the victory ; for every now and then a 
horse overcome by the violence of the shocks he 
received, was observed to disappear under the surface 
of the water. Some horses, however, rose again, and 
though exhausted by fatigue gained the shore in spite 
of the exertions of the Indians, where they stretched 
themselves out on the ground. I remember a superb 
picture of a horse entering a cavern and terrified at the 
sight of a lion. The expression of terror there depicted 
was not greater than that which we witnessed in this 
unequal contlict ; in less than five minutes two horses 
had succumbed, and were drowned. The eel, more 
than five feet long, glides under the belly of the horse 
and by a discharge of its electric organs attacks at once 
the heart, the viscei'a, and the gastric nerves. After 
such a commencement I was afraid that the fishing 
would end very tragically indeed; but the Indians 
assured me that it would soon terminate, and that the 
first assault of the Gymnotes was chiefiy to be dreaded. 
In fact after a time, the eels resembled discharged 
batteries. Their muscular motion continued active, but 
they had lost the {)ower of giving energetic shocks. 
When the combat had endured for a quarter of an hour 
the horses appeared to be less in fear; they no longer 
bristled up their manes, and their eyes became less 
expressive of sttffering and terror. They were no 
longer seen to fall backwards, and the Gymnotes swim- 
ming with their bodies half out of the water, were now 
flying from the horses and making for the shore. The 
Indians now began to use their harpoons, and by means 
of long cords attached to them drew the fish out of the 
water, without receiving any shock so long as the cords 
were dry.” Professor Faraday made experiments on 
two Eleciric Eels that were brought to London and 
kept in the Adelaide Gallery. By the galvanic currents 
of the fish, needles were magnetized, heat was evolved, 
an electric spark was obtained, and chemical decom- 
positions efl'ected ; in short, the absolute identitj' of the 
nervous currents of the Gymnote with those of a gal- 
vanic battery or Leyden jar was completely established. 
Professor Owen says that when he grasped the head of 
the Gymnote with one hand and the tail with the other, 
he received a stroke which was most painfully felt at 
the wrists, the elbows, and across the back ; but Pro- 
fessor Faraday showed that the nearer the hands were 
together within certain limits the less powerful was 
the shock, which was given by the parts of the fish only 
that intervened between the hands : the current was 
always from the head towards the tail. When the two 
examples of this fish were brought to England in 1842, 
neither of them weighed above a pound, but in 1848 
one of tliem had attained to forty, and the oilier to fifty 
pounds, so that each of them had gone on nearly doub- 
ling its weight in each succeeding year. So common 
is the Gymnote in the neighbourhood of Uritucu, that 
a route at one time much frequented had been aban- 
doned in consequence of the number of mules killed by 
these fishes every year in fording a stream that crossed 
the way. 
Family VII.— HETEROPYGIANS. 
With this family we commence the secondfsub-order 
of Malacopteres, or that which has ventrals; and as 
these fins are when present in this order always situated 
on the belly and are not closely connected to the sca- 
pulo-coracoid arch, the sub division has been named 
Ahdominales, or Abdominal Malacopteres. The very 
forward position of the vent, on the throat, is a char- 
acter which the Heteropygians possess in common with 
the Gymnotids, and from which they derive their appel- 
