When the embryo is adequately developed it hatches , i.e. breaks out of the egg 's shell .
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 embryo hatches , i.e. breaks out of the egg 's shell .
Eggs laid on land or in nests are usually kept within a warm and favorable temperature range while the embryo grows .