The pharyngula stage (PZ Myers, Pharyngula)

"The pharyngula stage: the pharyngula is a vertebrate embryo that has assembled the outlines of the body plan. It has the key features of vertebrate morphology -- a post-anal tail, a notochord, a dorsal neural tube, a segmented musculature, and an array of branchial arches ("gill" arches). The major organs have begun to form."

(Click here to go to post)