There are a great many tropical American pond-fish which share these adventurous gipsy habits of the pretty little Callichthys.  Though they belong to two distinct groups, otherwise unconnected, the circumstances of the country they inhabit have induced in both families this queer fashion of waddling out courageously on dry land, and going on voyages of exploration in search of fresh ponds and shallows new, somewhere in the neighbourhood of their late residence.  One kind in particular, the Brazilian Doras, takes land journeys of such surprising length, that he often spends several nights on the way, and the Indians who meet the wandering bands during their migrations fill several baskets full of the prey thus dropped upon them, as it were, from the kindly clouds.

Both Doras and Callichthys, too, are well provided with means of defence against the enemies they may chance to meet during their terrestrial excursions; for in both kinds there are the same bony shields along the sides, securing the little travellers, as far as possible, from attack on the part of hungry piscivorous animals.  Doras further utilises its powers of living out of water by going ashore to fetch dry leaves, with which it builds itself a regular nest, like a bird’s, at the beginning of the rainy season.  In this nest the affectionate parents carefully cover up their eggs, the hope of the race, and watch over them with the utmost attention.  Many other fish build nests in the water, of materials naturally found at the bottom; but Doras, I believe, is the only one that builds them on the beach, of materials sought for on the dry land.

Such amphibious habits on the part of certain tropical fish are easy enough to explain by the fashionable clue of ’adaptation to environment.’  Ponds are always very likely to dry up, and so the animals that frequent ponds are usually capable of bearing a very long deprivation of water.  Indeed, our evolutionists generally hold that land animals have in every case sprung from pond animals which have gradually adapted themselves to do without water altogether.  Life, according to this theory, began in the ocean, spread up the estuaries into the greater rivers, thence extended to the brooks and lakes, and finally migrated to the ponds, puddles, swamps and marshes, whence it took at last, by tentative degrees, to the solid shore, the plains, and the mountains.  Certainly the tenacity of life shown by pond animals is very remarkable.  Our own English carp bury themselves deeply in the mud in winter, and there remain in a dormant condition many months entirely without food.  During this long hibernating period, they can be preserved alive for a considerable time out of water, especially if their gills are, from time to time, slightly moistened.  They may then be sent to any address by parcels post, packed in wet moss, without serious damage to their constitution; though, according to Dr. Guenther, these dissipated products of civilisation prefer to have