I researched sexual reproduction in penguins. The male reproductive tract is made up of four principal parts, the testes, the epididymis, the ductus deferens and the sperm storage location near the cloaca. Like in most birds the female has only one ovary. This ovary produces ova that over a period of time of receptivity increase to 1000 times their original size. The basic female reproductive tract includes the ovary, the magnum, the uterus, the uterovaginal junction, and the oviduct.
Ovulation occurs and an ovum is released into the body cavity, the ovum is swept in the infundibulum by finger-like projections called fimbria. The maturing ovum moves into the magnum where it encounters the sperm. Fertilization occurs and the zygote continues to travel down the female reproductive tract. In the isthmus of the tract the zygote or "egg" continues it's travels, and the shell of the egg begins to form. All the while the size of the yolk sac and egg are increasing. Once the egg reaches the uterovaginal junction, the shell hardens and is then passed into the world though the cloaca.
The picture to the left is of an early embryo, at this stage the embryo is overwhelmed by the yellow yolk sac. Within a few days, the embryo grows in size to resemble something like an animal form. Incubation of the eggs varies in different species but is averaged at 62-67 days.
Mating behaviors of Penguins are interesting. The male makes his intentions known by offering a pebble. This is done to suggest the building of a nest, if the pebble is rejected then the penguin was either an unready female or another male. It is entirely up to the females to select the males, and it is quite usual for the female to pick the same male from the preceding season. .
Young Penguin chicks are very dependent on their parents for care. During incubation the mother penguin leaves the male alone to incubate the eggs while she goes out to the sea and feeds.