Discovery reports (1962) Discovery reports discoveryreports31inst Year: 1962 442 DISCOVERY REPORTS compared with the estimated cumulative frequencies of ovulations, the upper limit of the shaded portion representing a corpus luteum life of 15 days and the lower representing a life of 20 days. It is apparent that there is a reasonably good correlation between these curves, and a cumulative curve of ovulations may be taken to represent the entry of 'resting' females into the antarctic population. The best agreement is obtained if the centre of the shaded area, corresponding to a corpus luteum
Discovery reports (1962) Discovery reports discoveryreports31inst Year: 1962 442 DISCOVERY REPORTS compared with the estimated cumulative frequencies of ovulations, the upper limit of the shaded portion representing a corpus luteum life of 15 days and the lower representing a life of 20 days. It is apparent that there is a reasonably good correlation between these curves, and a cumulative curve of ovulations may be taken to represent the entry of 'resting' females into the antarctic population. The best agreement is obtained if the centre of the shaded area, corresponding to a corpus luteum life of 17-18 days, is used. Up to January there is fairly close agreement, but after this the numbers of non-pregnant adult females in South Georgia waters fall off. Probably very small numbers arrive in the Antarctic after March. 1000- > u z Ul a ui a. 500 D J MONTHS Text-fig. 49. Thick line, catch of non-pregnant females, South Georgia 1927-35, from Text-fig. 48. Shaded area represents estimated cumulative frequency of ovulation for corpus luteum life of 15-20 days. See text for explanation. According to these calculations 50 of non-pregnant females are south of the Antarctic Convergence by mid-December, and almost all have arrived by the end of March. As regards the true monthly frequency of this summer ovulation, December may, therefore, be considered as the median month. This is in reasonably close agreement with the cycle of ovarian activity in pregnant females, which shows a peak in November/December (see p. 348, Text-fig. 4). Pregnant females enter antarctic waters about a month in advance of non-pregnant females (Text-fig. 486), and it would seem that in this class also ovarian activity is correlated with the southward migration. It will also be remembered that a similar correlation was demonstrated for some nulliparous females at puberty. We will return to this interesting point later (p. 450). The main purpose of this brief discussion has been to show that the
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