Functional polyovuly in the sei whale Balaenoptera borealis lesson

Abstract

ON September 1, 1962, a female sei whale, 50 ft. long' was landed at Donkergat whaling station, Saldanha Bay, South Africa. It was found to be pregnant, with two fœtuses in the same cornu of the uterus but within separate fœtal membranes. There was only one corpus luteum of pregnancy in the ovaries so the twins were at first presumed to be monozygotic. However, of the two fœtuses, one proved to be male, 38 cm long, weighing 746 g, and the other female, 39.5 cm long, weighing 737 g (Fig. 1. Scale Combining double low line 20 cm). © 1963 Nature Publishing Group.