This article is about egg strata eggs. For eggs as food, see Egg as food.

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Eggs of various birds, a reptile, various cartilaginous fish, a cuttlefish and various butterflies and moths. Diagram of a chicken egg in its 9th day. Reptile eggs, bird eggs, and monotreme eggs are laid out of water and are surrounded by a protective shell, either flexible or inflexible.

Eggs laid on land or in nests are usually kept within a warm and favorable temperature range while the embryo grows. When the embryo is adequately developed it hatches, i. Whale shark eggs typically hatch within the mother. Reproductive structures similar to the egg in other kingdoms are termed “spores,” or in spermatophytes “seeds,” or in gametophytes “egg cells”. Several major groups of animals typically have readily distinguishable eggs. Larval stage in lampreys, direct development in hagfish. Larval stage, ovovivipary in some species.

Medium-sized mesolecithal eggs in all species. Tadpole stage, direct development in some species. Large macrolecithal eggs, develop independent of water. Large to very large macrolecithal eggs in all species, develop independent of water. The young more or less fully developed, no distinct larval stage.