<P> 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.e. breaks out of the egg's shell . Some embryos have a temporary egg tooth they use to crack, pip, or break the eggshell or covering . </P> <P> The largest recorded egg is from a whale shark, and was 30 cm × 14 cm × 9 cm (11.8 in × 5.5 in × 3.5 in) in size . Whale shark eggs typically hatch within the mother . At 1.5 kg (3.3 lb) and up to 17.8 cm × 14 cm (7.0 in × 5.5 in), the ostrich egg is the largest egg of any living bird, though the extinct elephant bird and some dinosaurs laid larger eggs . The bee hummingbird produces the smallest known bird egg, which weighs half of a gram (around 0.02 oz). Some eggs laid by reptiles and most fish, amphibians, insects and other invertebrates can be even smaller . </P> <P> Reproductive structures similar to the egg in other kingdoms are termed "spores," or in spermatophytes "seeds," or in gametophytes "egg cells". </P> <P> Several major groups of animals typically have readily distinguishable eggs . </P>

The egg of an animal is most like which part of a plant