142 



Mai.acopterous Apodals.- 



-FISHES.- 



-Gymsotids. 



down by mucus. In the woodcut it is shown partially 

 disengaged. 



Professor Ilyitl has shown that Gi/mnarchus 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. 



Fi! 



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 



Suarp-nosed Thong-fish (Steruarchus oxyrhir.chus). 



upper pair and a slender lower pair laid along the base 

 of the anal fin. Each bundle is constructed of parallel 

 membranes and Ijorizontal 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 highly 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 be taken without risk. Time and repose are 

 needed before the batteries are ready to act again. 

 The hoi'ses 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 conflict; 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 visceia, 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 chiefly to be dreaded. 

 In fact after a time, the eels resembled discharged 

 batteries. Their muscular motion continued active, but 

 they had lost the power 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 suffering and terror. They were no 

 longer seen to fall backwai-ds, 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 liarpoons, and by means 

 of long cords attached to them drew the fish out of tlie 

 water, without receiving any shock so long as the cords 

 were dry." Professor Faraday made exi)eriments on 

 two Elecirio Eels that were brought to London and 

 kept in the Adelaide Gallery. By tlie galvanic currents 

 of the fish, needles were magnetized, heat was evolved, 

 an electric spark was obtained, and chemical decom- 

 positions efi'ected ; in short, the absolute identity 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 witliin 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 Ihera had attained to forty, and the other 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. 



F.uiii.Y VII.— HETEROPYGIANS. 



With this fiimily we commence the second sub-order 

 of Malacopteres, or that wliich 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 

 Abdominales, or Abdominal Malacopteres. The very 

 forward position of the vent, on the throat, is a char- 

 acter which the Ileteropygians possess in common with 

 the Gymnotids, and from which they derive their appe!- 



