Abstract
In the golden hamster (Mesocricetus auratus) the gestation period and the loculus size of the gravid uterus from day 6 to day 15.5 (parturition) of gestation as well as the weight, width (umbilicus back) and length (crown rump) of the embryos from day 9 to the parturition were measured. The results obtained were as follows: The gestation period of the golden hamster was 15 days and 15±3 hr post coitum. The average values of the length (in the direction of uterine long axis) and width (mesometrial antimesometrial axis) in the loculus of the gravid uterus were 0.39 cm and 0.56 cm at 6 days, and 2.42 cm and 1.74 cm at 15.5 days (parturition), respectively. The average values of the crown rump measurements, width (umbilicus back) and weight in the hamster embryos were 0.42 cm, 0.24 cm and 0.026 g at 9 days, and 2.40 cm, 1.39 cm and 2.272 g at 15.5 days (parturition), respectively. The loculus size of the gravid uterus, the crown rump measurements and width (umbilicus back) of the embryos in the period from day 13 to day 14 of gestation were markedly increased in comparison with any other period, and the weight increase of the embryos occurred rapidly from day 13 of gestation. The shape of the loculus during the gestation was ovoid (mesometrial axis) until the end of 10 days converged to the spherical form and thereafter changed gradually to the ovoid form in the direction of uterine long axis contrary to the previous days.