Position of the embryos of American mink in the fetal chamber at different stages of development]

The spacial position of American mink embryos is characterized by regular changes and is associated with the development and formation of provisory embryonic organs and the uterus. After the implantation the longitudinal axis of the embryo's body lies perpendicularly towards the long axis of the uterus horn. From the end of the 22nd day till birth the embryo moves along the antimesometral side of the fetal chamber by rotation counter clockwise relative to the point of attachment of the alantois stalk. On the 20th day prior to delivery the embryo's body bent as a coil takes a vertical position its fore-part is disposed in the yolk sac cavity, and the hinder part is in the exocoelom. During 17 days before birth the embryo "rolls out" from the yolk sac cavity and occupies the low position in the longitudinal posture of the body. During the following 6 days the prefetus moves towards the opposite side wall of the fetal chamber, takes the upper position and keeps a longitudinal position till the end of the embryonic life.