African lung-fishes. The massive body is invested with heavy bony scales, but these primitive 

 bony fishes are not adapted to an aerial existence and must keep to the rivers and marshes, while 

 avoiding dried-up conditions. Like the North American bowfins, they build large nests of 

 about a yard in diameter in the reeds by crushing the plants with the tail and the weight of the 

 body. The females lay numerous eggs which soon hatch. The larvae, which have large gill 

 filaments of a fine red colour, reach the surface and swim around in the enclosure of the nest. 

 The next day they form into a round-shaped school in the middle of this little pool. Then they 

 shed the external gills and on the fourth day they venture outside, being watched over by the 

 parents. A little later they are able to lead an individual life. 



At the mouths of the great rivers and along all the African coast from Gambia to Angola 

 extends the littoral belt of mangroves, which Aubert de la Riie has described in his book " The 

 Tropics ". Crabs scuttle around the roots on which oysters are growing, and in this tangle 

 of plants, numerous fishes swim around. This is the home of cat-fishes, which root in the mud 

 with their many barbels (Ariiis, Clarias, Chrysichthys, Galeichlhys). Not far away swim 

 thread-fins (Polynemus quadrifilis). On the sides of the head they have a gelatinous mask 

 and their pectoral fins carry long thread-like rays which are used for exploring in the mud. 

 They are excellent food fishes of great economic importance to the riparian populations. 

 Grey mullets are also very numerous. All these fishes fear the passing of the mangrove swamp 

 predators, the barracudas, the becuna of the West Indies. These large voracious beasts with 

 their very elongated bodies, which may be more than 6 feet in length, stir up much the same 

 kind of fright in brackish waters that pikes do in fresh waters. Native fishermen fear barra- 

 cudas at least as much as they do sharks and merciless struggles are waged in the shade of the 

 mangroves. 



Descending the Amazon. 



In the torrents that come from the eternal snows, under the cold, unflinching stare of condors 

 and black eagles, are fragile fishes that are adapted to the unusual surroundings of mountain 

 streams. They live among the towering peaks of the Andes and cling to the rocks, where they 

 withstand the violent shocks of the waters. They are a line of evolution of the mailed cat- 

 fishes (loricariids), which live in tropical rivers. But in their ascent to the deep basins 

 hollowed out by whirlpools, where they find shelter from voracious enemies, they have lost . 

 their defensive armouring. By an enlargement of the lips the mouth of Cyclopiiim has been 

 turned into a powerful sucker and the lower surface of the pelvic fins has been similarly modified. 

 With this double means of support the fish are able to struggle against the currents and to pro- 

 gress while clinging to the vertical walls of rocks. The prenadillas (Arges, Stygogenes) pene- 

 trate into the subterranean streams of the cordifiera, which run in volcanic fissures. An eruption, 

 which made them leave their inaccessible retreats and move with the torrents of mud and 

 cinders coming out of the craters, first brought them to light. 



Numerous streams run down the slopes of the great mountain chain and unite in the Braz- 

 ilian plain to form the great river. In the shade of the forest at the rainy season all these 

 streams overflow and when the floods retreat, marshes and watercourses are left under the cover 

 of the trees and lianas. Here are found loricariids that have kept their armouring. Some, 

 such as Acestra, have a tapering body ending in a tubular snout and look rather like the marine 

 pipe-fishes. Others, like the chaetostomids, are more heavily built and resemble the armed 

 bullheads or agonid fishes. Under the chin of the males there are outgrowths of the skin and 

 numerous barbels. They root in the river mud by the side of cascaduras (CalUchthys palealus), 

 cat-fishes invested with a carapace formed from a double row of overlapping plates that are 

 joined at the level of the lateral line and arranged according to the body segments. 



Another cat-fish, Doras, leads a more active life. It is unarmoured and moves along the 

 river banks at great speed, running on its pectoral fins, which are assisted by vigorous beats 



136 PeltnatochroTnis kribensis. Southern Cameroons. 



Symphysodon discus. Amazon. Photographs V. Six, 

 Aquarium du Zoo d'Anvers. 



