Day 5: Reproductive system and differentiation of sex appear; thymus, bursa of Fabricius, duodenal loop begin; chorion and allantois begin to fuse; mesonephros begins to function; first cartilage present.
Day 7: Digits appear; comb growth begins; egg tooth begins; melanin produced; absorption of mineral from shell begins. Chorioallantois is attached to inner shell membrane and growth around the inner surface is progressing.