The most obvious way is to put it in an incubator. and see if there is any growth. However, this is not the. most practical way when you are selling eggs for human. consumption. In that case, the best way to tell a fertile. egg is to examine the germ on the egg's yolk to see if. it has divided. The germ is also called the Blastoderm and is. where the baby chick begins to grow. The germ is. located on the surface of the yolk and appears as a light. spot.