EN
There were examined 132 arabian mares for 3 years: 1987, 1988 and 1989. The activity of ovaries and the developmental phases of the Graaf’s vesicle were examined in the preparturient period. Between 13 and 30 days since ovulation 320 measures of the embryonic vesicle were performed. A mean diameter of the vesicle in individual days is vizualibed in Table 1. In the corpus of the uterus embryo was localized in 6 cases, in the left horn of the uterus in 138 (45.69%) and in the right horn in 134 cases (44.37%). The shape of the embryonic vesicle was spherical up to the day 16 after ovulation and at the day 18 it lost its spherical form. After 23 days since ovulation the embryo was located in the middle part of the vesicle. At the day 50 it was localized at a lower edge of the vesicle and a spontaneous movement was recorded. Heart pulsation was noted between 23 and 30 day. In the breeding season 1989 a bigeminal pregnancy was diagnosed in 3 mares, 2 embryonic vesicles were situated in separated horns and one in one horn. In two mares two bigeminal foetuses have been resorbed completely up to day 30 after ovulation and in one mare the embryo persisted at the left horn and the foetus in the right horn was absorbed between 25 and 30 day.