These fishes have "become dwarfed and concentrated, taking the place in their respective habitats which the darters occupy in the waters of the Mississippi valley. By the same process of 'analogous variation' the cichlids of South America parallel the sunfishes of the United States, although in structure and in origin the two groups are diverse." Dr. Jordan tells us that the trout of the Pacific coast came to America from Asia, and gradually spread eastward and southward until now it is found in all the streams of the Rocky Mountains, the Sierra Nevada, the Cascades and the Coast range. It is but a short distance from Kamchatka to Alaska, and this distance is traveled by trout to this day; once over, a fish able to spend much of its time in salt water could easily colonize all our coast streams. Whether or not all of our Pacific trout are descendants of one species, the cut-throat trout, is more or less uncertain, though it is quite certain that all have descended from not more than two or three species. In many places they have been able to pass from the head waters of one river to that of another, just as they now pass from the head waters of the Columbia to the Missouri by the way of Two Ocean Pass. The ancient lakes, Lahontan and Bonneville, no doubt assisted them in their migrations. Since these have disappeared each colony has had to remain more or less isolated. In time they have become somewhat changed, to better adapt themselves to their new environment. These changes have developed certain peculiar characters, by means of which we can distinguish one kind of trout from another, just as the farmer distinguishes his Berkshire from his Poland China. Spread, as the trout are, over such a large area, in such an immense variety of streams and lakes, and with a vertical range of over one thousand feet, we would certainly expect as large a number of species and varieties of trout to be developed as we find at present in the streams of our west coast. Fishes are found in the deepest parts of the ocean. Some of these are peculiar to the deep waters, none of the shore fishes resembling them. On the other hand, many deep sea fishes belong to families well represented in the shallow water. The flounders are found in water at all depths, and the same is true of the bat fishes, rock fishes and other shore fishes. It is easy to understand how these fishes have found their way to the deep water. It was either to escape their enemies or to extend their range for some reason; as Mr. Garman puts it, "They have slid down," as it were to the bottom of the ocean.