Note 44 — THE STEPPES OF INNER AFRICA.

[Note 44] p. 183.—The mud-fish.

This remarkable animal (Protopterus) is one of the Double-breathers or Dipnoi, a member of a small class between Fishes and Amphibians, represented by three genera—Ceratodus in Queensland, Lepidosiren in Brazil, and this Protopterus in Africa. They differ in many ways from other fishes, being physiologically intermediate between Fishes and Amphibians. Hundreds of specimens have been brought within their ‘nests’ from Africa to Europe. Brehm speaks of the complete enclosure of the capsule, but this is now known to communicate with the outer world by a tubular passage through the mud. At the foot of this tube the mud-fish keeps his nostrils. The lung is a specialization of the swim-bladder which is present in most fishes.