Although the jacks lie in the quiet ponds most of the time, yet some of them travel about a great deal, especially the smaller ones ranging from one to two pounds. These will leap a bay or dam if it interrupts their voyaging down the stream. I have seen a young jack, about a foot long, leap over a bay, and fall three or four feet on to the stony floor below, the stones scarcely covered with water. The jack shot himself perhaps two feet, and fell on his side on the stones; there he lay quietly a minute or so, and then gave a bound up, and, lighting in the current, went down with it. A small jack like this will sometimes go out into the irrigated meadows, following the water-carriers for a long distance. In quiet, sheltered places, where the water is clear but does not run too swiftly, the `minnie,' as the stickleback is locally called, makes its nest beside the bank. A small hole in the sand is excavated, and in this are laid a number of tiny fibres such as are carried along by the stream, resembling a miniature faggot. On these fibres the ova are deposited, and they are then either purposely partly covered with sand by the minnie, or else the particles that are brought down by the current gather over the bundle of fibres and conceal it, excepting one small spot. There several of the slender roots seem to slightly project, and they are kept clear of mud or sand so as to answer the purpose of a doorway. I have watched these operations many times, but never saw the minnie attempt to enter the nest; indeed, he could not have done, so, the opening not being large enough. When the nest has reached this stage of completion it is easy to discover, because the stickleback keeps watch before it, and at that season his breast is of a bright crimson hue. He guards the nest with the greatest care, and if he is tempted away for a minute by some morsel of food he is back again immediately. If a tiny twig or fibre comes along and threatens to catch against the nest, he removes it in his mouth, carrying it out into the stream that it may be swept away. He also removes the sand whenever it begins to accumulate overmuch. It would seem as if a current of fresh water were essential to the ova, and that that is why the opening of the nest is so carefully kept from becoming choked up. After a while the fry come forth--the most minute creatures imaginable, mere lines about half the length of the fingernail. They play round the opening, and will retreat within if alarmed.