There is an interesting family of fishes in our fresh waters known as Minnows; these fishes are too small and too full of bones to become a favorite for the table. They are the most helpless of all our fresh water fishes, being soft, and, as they are slow swimmers, they become an easy prey to larger fishes, and form a large part of their food supply. They have been constantly driven into smaller streams and shallow water, until they have become exceedingly dwarfed. Their only use in the economy of fish life seems to be to assimilate small organisms, converting them into such shape that they can be taken by the larger fishes. Now the Minnows of all the United States east of the Rockies are small and, except in case of a few species, they are less than six inches in length. The predatory fishes, such as the Sunfishes and Perches, Pike and Pickerel, are their worst enemies. In the Rocky Mountains there are none of these fishes, and many minnows there grow to a length of two feet or more. The only enemy of importance they have is the trout, but the minnow finds a more congenial climate in the larger bodies of water, too warm for the trout. The struggle for existence has been a severe one, especially so in our streams where species of fish are the more numerous. It has greatly limited the growth of most species beyond an average size, and is in many places responsible for the fact that often a species may become dwarfed in certain bodies of water. In the Salmon river in Idaho it was not an uncommon thing to catch trout of three or four pounds weight. In the smaller tributaries and in the smaller mountain lakes it was unusual to catch one weighing over one-half pound, the average being less than one-fourth pound. I have no doubt that many of those from the small lakes of one-half pound were as old as the large ones taken from the Salmon river. Fish eat and grow very irregularly. The average size of individuals, which we would ordinarily call adults, for some species, is different in different bodies of water. Their growth is influenced largely by the size and depth of the body of water in which they live, also by its temperature and the amount of suitable food it contains. The value or extent of each of these influences is imperfectly understood.