Any barrier which prevents or hinders fishes in their movements from one body of water to another will separate two more or less well-marked fish faunas. These barriers may be mountains, or shallow water, as in the case of deep sea fishes; deep water, as in case of shore fishes; muddy or alkaline water, or water of different temperature. Temperature no doubt has far more influence in governing the movement of fishes than is generally believed. It plays an important part in guiding salmon up stream to their spawning beds. It explains why they reach the head waters of some streams and spawn earlier than in similar streams not far distant, but of different temperature. If you would know to what extent fishes of one region differ from those of another, study well the barriers between the two regions, learn to what extent and how long they have existed, consider the age geologically of the two regions, and how fishes may have migrated to one or the other, and in a general way you will have the key to the situation, which a careful study of the fishes is quite sure to verify. Seth E. Meek. [Illustration: LOUISIANA TANAGER. (Piranga ludoviciana.) Life-size. FROM COL. CHI. ACAD. SCIENCES. COPYRIGHT 1900, BY A. W. MUMFORD, CHICAGO.] THE LOUISIANA TANAGER. (_Piranga ludoviciana._) The family of Tanagers is remarkable for the number of species, the gaudy coloring of many and the interesting fact that they are confined to the Americas and the adjacent islands. Dr. Ridgway says, "that the five families of Neotropical birds, which are represented by the greatest number of species, are absolutely peculiar to America, these families being the Tanagers, Tyrant Flycatchers, Wood-hewers, Ant Thrushes and Humming-birds. None of these families have even true representatives in any part of the Old World." The family of Tanagers includes approximately three hundred and eighty species, of which not more than ten per cent. have a range extending as far north as Southern Mexico, and only four, or at the most five, species are known to the United States. Of these only two, the Scarlet Tanager and the Summer Red-bird, are generally known as far north as Canada. The Tanagers make their home in the trees, and, being of a retiring disposition, are more numerous within the bounds of the forest. During the breeding season they retire still further into the interior. No wonder that they are more numerous in tropical regions, where the luxuriant foliage of the forests furnishes them with a safe retreat, and where there is an abundance of food suited to their taste. This tendency to avoid the society of man has made the study of their habits much more difficult, and but little has been recorded except that which pertains to the more northern forms.