260 



ICHTHYOLOGY. 



Classifica- out. x])e Callichth/s are monogamous, both male and 

 tion— ila- fg„,ale remaining by'the side of the nest, and watching it 

 acop eri^ carefully. A specimen of the nest, spawn, and fish, exists 

 ^""^ in the College of Surgeons of London. 



Arges, Brontes, and Astroblepus, are three forms of 

 Siluroids of exceeding interest. They are some of the 

 small fishes which issue from the bowels of the active vol- 

 canoes of South America, and are carried into the plains 

 beneath by the torrents of muddy water, whicli these moun- 

 tiins vomit forth. They issue from Cotopaxi, Tungurahua, 

 Sano-ay, Imbaburu, and Cargueirazo, a phenomenon first 

 properly communicated to the scientific world by the illus- 

 trious Humboldt. They are expelled from craters or from 

 lateral openings, always 16,000 or 17,000 feet above the sea, 

 and the plains themselves into which these clayey streams 

 descend, lie at least at half that height. Humboldt ascer- 

 tained, by consulting the records of the neighbouring towns, 

 that in 1691 Imbaburu threw out myriads of these fish in 

 the neighbourhood of the city of Ibarra, and has continued 

 to do so down to a late period. Cotopaxi also covered the 

 estate of the Marchese di Salvategre with so large a quan- 

 tity of these subterranean Siluroids, that the odour of their 

 decaying bodies spread far and wide, so much so indeed, that 

 the pestilential fevers which then prevailed were attributed 

 to these putrid exhalations. In the eruption of 1698, when 

 the peak of Cargueirazo fell in, vast quantities of these fish 

 were brought down by the muddy and smoking streams 

 which the mountain poured forth. INI. Humboldt has pro- 

 posed many questions bearing on these facts, without of- 

 fering a solution. What streams of water, or what lakes 

 exist in the cavernous recesses of these moimtains? How 

 does it happen that water submitted to so high a tempera- 

 ture retains air enough to support the life of such multi- 

 tudes of fishes? How do animals with flesh so soft escape 

 being cooked as they pass far, and for a long time, through 

 the smoke which envelopes the streams of mud that issue 

 during the eruption ? These fish are called in the country 

 prehcidillas, a name not confined to a single species. The 

 one that Humboldt specially described is the Arges ajclo- 

 jmin, oiiginally named by him Pitnelodus ryclopum. 



In Clarias the nape is not armed, and the development 

 of the bones of the head is lateral ; the suborbitars, which, 

 in the rest of the family, are mere slender tubes, in this 

 genus give extension to the helmet, and tlie supratem|)0- 

 rals which, in most fishes are very small, and in the greater 

 number of Siluroids are imperceptible, here become enor- 

 mously large, and coalesce on the sides of the cranium, 

 with the prefrontal, frontal, po^tfrontal, and mastoid. An 

 apparatus lor holding water in the vicinity of the branchiae 

 exists in this genus, and its near allies analogous to that of 

 the AnabasidcE. The Clarias aiiguillaris of Hasselquist 

 has been by some writers on Egypt considered to be the 

 Alabes of Strabo, cited by Archestratus, as one of the sa- 

 cred fishes of the Nile. It is now known on the banks of 

 that river by the name of Harnwuth, or, as Sir Gardner 

 Wilkinson writes the word, Karmoot. It was either wor- 

 shipped, the latter author says, in the Thebai'd, or was con- 

 nected with one of the genii of the Egyptian Pantheon, 

 who appears under a human form, with the head of this 



Fi?- 85. 

 Plotosus microceps. 



fish in the sculptures of the Diospolite tombs. In Lower 



Egypt the Karmoot was caught for the table; but there is Classifica- 

 no evidence of its having been eaten in the Theba d, which "o" — Ma- 

 may be an argument in favour of its sacred character. lacoiiten. 



Plotosus is a genus of the Siluroid family which frequents ^""^/^"^ 

 the seas of southern Asia and the eastern coasts of Atiica, 

 and from thence southwards to Australia, where there are 

 several species. One of these, PI. microceps, is represented 

 by the annexed woodcut, and the lips by figure oO. 



Aspredo differs greatly from the rest of the Siluroids, 

 and from other osseous fishes, in the rudimentary and im- 

 moveable condition of its gill-flaps, the three pieces that 

 generally perform the office of a valve to the gill-openings 

 being mere vestiges confluent with the preopercuhmi in 

 such a way, that the opening and closing of the aperture 

 does not depend on the tympanico-opercular apparatus. 

 The mouth likewise is peculiar, the premaxillaries being 

 articulated longitudinally, so that the orifice is a slit in the 

 axis of the fish, with teeth in its posterior part only. Some 

 curious sucker-like appendages are formed on the females at 

 certain times by the expansion of pores and development 

 of filaments on their edges. These are not found in the 

 males. Bloch named a species Cotylephorus which had 

 these organs, and M'Clelland has characterized a genus 

 chiefly by their existence. Their presence, however, ap- 

 pears to be temporal, and to extend to the females of all 

 the species. 



Malapterurus electricus, Lacep. The electric powers 

 of this fish were noticed by Adanson in 1756, but in Pur- 

 chas' Pilgrims, there is a much earlier account of it ex- 

 tracted from the narrative of Baretus and Oviedo, dated 

 1554. It is there said, that there exists in the Nile a fish 

 (called by Purchas a torpedo), which, if held in the hands, 

 causes on the slightest movement a severe pain in all the 

 arteries, nerves, and joints of the body. In the same work 

 Richard Jobson is reported to have perceived in the River 

 Gambia a fish like an English Bream, but thicker, which, 

 on one of the sailors taking hold of, he instantly cried out 

 that he had lost the use of his hands and arms. Another 

 sailor, on to\iching the fish with his foot, felt his legs be- 

 numbed. This was in 1620. Aiihe Malopteriirus ahoxmAi 

 in the Nile and in Senegal, and the torpedo has no resem- 

 blance to a Bream, the former was doubtless the fish to 

 which Purchas alluded, notwithstanding his use of the name 

 Torpedo. Rudolphi' has given a detailed description, with 

 figures of the electric organs of this fish. In the great 

 i\ork on Egypt by Geoflroy (PI. XII., 2), there is the figiire 

 of a Malapterurus opened to show the viscera, but by a 

 singular inaccuracy the fish is re]n'esented as scaly ; now 

 there are no scales whatever on this fish, and no fish known 

 to possess electric powers has either scales or spines. '1 he 

 Torpedo, the Gi/timotus, and the 3Ial(ipterurvs, have all 

 naked skins. The Tetrodon electricus is also destitute of 

 spines on the skin', though all its congeners have skins as 

 bristly as those of a hedgehog. 



M. Valenciennes, examining theelectric organs of the Ma- 

 lapterurus with a full knowledge of h hat had been previously 

 observed by Geoffrov and Rudolphi, describes it as being 

 composed of a thick layer of spongy cellular tissue, lying im- 

 mediately under the skin, and framed of thin interlacing leaf- 

 lets, filled with a gelatinous fluid, and lined on its internal 

 fate by a silvery aponeurosis to which it adheres strongly. 

 This aponeurosis extends from the liirehcad and the gill- 

 openings to the posterior end of the anal, and is divided into 

 lateral halves by a membranous raphe that appears on the 

 dorsal and ventral aspects. LTnder this aponeurosis run the 

 great vascular and nervous trunks, whose branches pass 

 through it, to be expended on the cellular tissue. Then be- 

 neath this aponeurosis there is a peculiar membrane which 

 forms the subject of Rudolphi's Memoir. It consists of at 



1 Uehcr den Zitter-weU, Abh. Bcrl. Acad. vii. 



