** Pig: Blastocysts are 2mm spheres at day 10 of gestation. During the next 24-48 hours, they elongate to ~200mm in length. By day 16, the blastocyst reaches lengths of 800-1000mm. | ** Pig: Blastocysts are 2mm spheres at day 10 of gestation. During the next 24-48 hours, they elongate to ~200mm in length. By day 16, the blastocyst reaches lengths of 800-1000mm. |