OTHER DIPNOI

gills of the fish, which are adequate enough in favourable conditions. It is in fact exactly in the condition of a rather elderly tadpole. The very young tadpole has merely gills like a fish; later on, the lungs appear, while the gills persist; later still, the gills vanish and the lungs alone remain: it is, however, now a frog. Ceratodus remains for its whole life in the tadpole condition. It would not be a gross exaggeration to describe it as a huge scaly tadpole.

The Australian mud fish is one of those "friendless " creatures, a survival from past times, when creatures were apt to be a little less decided as to their relationships than at present. It is a link between fishes and amphibians. Ceratodus itself has not a tadpole; but its near allies, the African mud fish, Protopterus, and the South American Lepidosiren, have newly-hatched larvæ which are immensely like young tadpoles. Everybody must have noticed the way in which the tadpoles of our common frog hang on to the leaves of aquatic plants by their chin, which they press firmly thereto as the Red Queen pressed her chin upon the shoulder of Alice. A sucker achieves this anchorage, and the same sucker is present in the young mud fishes of America and Africa. The Paraguayan mud fish, once so scarce that it was represented in European museums by about three specimens, has long furnished a succulent meal in certain regions of South America. It has been brought home in abundance and carefully studied by Professor Graham Kerr; it is therefore not by any means unlikely that the visitor to the Zoo will have the opportunity of seeing side by side this creature and its Australian relative. In any case he will be practically. certain to have the chance of seeing Protopterus of Africa.