10. _Galaxias_ is equally represented in Southern Australia, New Zealand, and the southern parts of South America. _C._ Families identical in distant continents-- 1. The _Labyrinthici_, represented in Africa by 5, and in India by 25 species. 2. The _Chromides_, represented in Africa by 25, and in South America by 80 species. 3. The _Characinidæ_, represented in Africa by 35, and in South America by 226 species. 4. The _Haplochitonidæ_, represented in Southern Australia by one, in New Zealand by one, and in Patagonia by a third species. This list could be much increased from the families of _Siluridæ_ and _Cyprinidæ_, but as these have a greater range than the other Freshwater fishes, they do not illustrate with equal force the object for which the list has been composed. * * * * * The ways in which the dispersal of Freshwater fishes has been effected were various; they are probably all still in operation, but most work so slowly and imperceptibly as to escape direct observation; perhaps, they will be more conspicuous, after science and scientific inquiry shall have reached to a somewhat greater age. From the great number of freshwater forms which we see at this present day acclimatised in, gradually acclimatising themselves in, or periodically or sporadically migrating into, the sea, we must conclude that, under certain circumstances, salt water may cease to be an impassable barrier at some period of the existence of freshwater species, and that many of them have passed from one river through salt water into another. Secondly, the headwaters of some of the grandest rivers, the mouths of which are at opposite ends of the continents which they drain, are sometimes distant from each other a few miles only; the intervening space may have been easily bridged over for the passage of fishes by a slight geological change affecting the level of the watershed, or even by temporary floods; and a communication of this kind, if existing for a limited period only, would afford the ready means of an exchange of a number of species previously peculiar to one or the other of those river or lake systems. Some fishes, provided with gill-openings so narrow that the water moistening the gills cannot readily evaporate; and endowed, besides, with an extraordinary degree of vitality, like many Siluroids (_Clarias_, _Callichthys_), Eels, etc., are enabled to wander for some distance over land, and may thus reach a water-course leading them thousands of miles from their original home. Finally, fishes or their ova may be accidentally carried by waterspouts, by aquatic birds or insects, to considerable distances.