In some species, the embryos eat the remaining eggs or even other embryos while still developing in the uterus. (sciencedaily.com)
Mars therefore must be an embryo that for some reason stopped merging with other embryos and failed to become a full - size rocky planet. (sciencemag.org)
But Bernard Thisse, an embryologist at the Institut de Génétique et de Biologie Moléculaire et Cellulaire in Cedex, France, noticed something fishy: When head and torso organizer cells were grafted onto other embryos in zebrafish, the tail region never quite developed completely. (sciencemag.org)