Re: At what stage is egg's shape finalised?

Birds and many of the reptiles lay eggs with a hard (calcareous) outer shell. The shape of the shell vary with different species. Some are oval, some are more or less conical and certain others are spherical in shape. The shape of the egg has been evoled over millions and millions of years. Birds living in rocky terrain/mountain cliff lay eggs that are more or less conical in shape. This shape prevents the egg from rolling down a flat/inclined terrain. In contrast, birds that build cup shaped soft nests,lay eggs that are almost spherical in shape. In general, the shapes of the egg are suitably adapted for the different environment ("terrains") in which the eggs are laid. The egg producing structures - the ovary and oviduct are evoled in such a way that they help in making the "desired" shape in a perfect manner. The final shape of the egg is assumed in the oviduct.The oviduct that connects ovary and the cloaca does not have "powerful" musculature instead it has soft circular muscle that pushes the egg to the cloaca.