Jane Dawson, age 13, of Austin, Texas, for her question:

HOW LONG DOES IT TAKE EGGS TO INCUBATE?

Fertilization of a bird's egg takes place in the upper part of the oviduct of a female bird. Only one male cell fertilizes each female cell. The union of the male and female reproductive cells causes the development of the embryo. The fertilized cell starts to divide and many cell divisions are completed before the egg is laid.

The egg of the domestic hen must be kept at the proper temperature or incubated for 21 days before the chicks will hatch.

Most duck eggs incubate for 28 days but Muscovy duck eggs need 35 days. Turkey and guinea eggs must be incubated for 28 days.

Goose eggs must incubate from 32 to 35 days, quail eggs from 22 to 24 and pheasant eggs from 23 to 28 days, depending on the variety. The eggs may be incubated under hens or in incubators.

An egg is made up of the following: water, 65.5 percent; protein, 12 percent: fat, 11 percent; and minerals, 11.5 percent.