The chicken egg has been prepped for surgery – a pea-size hole cut in the shell and covered with sticky tape. And now Hans Larsson, a McGill University researcher, removes it from the incubator, places it under a microscope and prepares to operate. He gently peels off the tape and teases back the membranes that line the shell with tweezers. Through the eyepiece, he can see the tiny dot of a heart, steadily beating. He can also see the bud where he implants a milky bead doused in a protein. He hopes it will coax the embryo to grow a...