To repeat: _All_ life comes from an egg. You know how the eggs of fishes look as well as the fact that the shad roe you eat is a mass of eggs. The male shad is called the buck shad or the milt shad. The milt is the semen of the male shad. It is a milky-white substance. The little life-giving germs are hidden in this milk-like fluid. They are so small that it takes a powerful microscope to see them.
The eggs of the female cannot produce life unless the life germs of the male pass into them. This is true of all animals, including man. Every form of living thing has a different method of doing this, but the principle is the same for all. Let us first take the fishes.
Springtime is the season for all life to bring forth its kind. In the spring the fishes swim to their spawning or breeding places. They seek warm and generally still waters. The shad, for instance, swims up rivers until it finds the proper place. By this time the eggs are ready to be expelled from her ovaries, the sacks in which they have been forming all winter. As she lies still in the warm waters these eggs drop out in large quantities. Then she swims away, gradually making her trip down to the sea. At the same time that her eggs are ready to be deposited in the waters the male shad is filled with milt-fish semen. He is strong, vigorous, and never having wasted any of this seed he is able to give full life to the waiting eggs. He slowly swims over the floating eggs and the semen in him pours out. Once over the eggs each little life-germ wiggles through the outer lining of an egg and meets the true egg. At once these two, the female and male germ, are the beginning of a little fish. It takes some time, of course, for even the little fish to burst from its covering, for the growth from the two germ cells into a completely-formed, though tiny fish, occupies many days. But just as soon as it is ready to swim, out it comes.
The way the different kinds of fish protect their young until they can care for themselves, is an interesting study, but you can read all about such matters in your zoologies.
In breeding, or propagating, fish at the hatcheries, the eggs are squeezed out of the female and immediately after this has been done the milt from the male is squeezed out over them. This is never done except when both female and male fish are ready to deposit their eggs and sperm. By this method the little fish can be kept in confined waters, arranged according to their ages, and when old enough, be sent to replace fished-out streams.