. R P STAGE OF CYCLE Text-fig. 45. Mean diameters + 2 of corpus luteum, and six largest corpora albicantia of pregnant, lactating1, and ' resting' females plotted to a time scale so as to represent two sexual cycles. See text for explanation. The mean size of the largest corpus albicans in lactating females is 5-58 cm.; the mean size of the largest corpus albicans in lactating females which are also pregnant (not given in Table 20) is 5-61 cm., and in' resting' females it is 5-57 cm. These mean sizes are not significantly different, and if we suppose that there has been not more than one
. R P STAGE OF CYCLE Text-fig. 45. Mean diameters + 2 of corpus luteum, and six largest corpora albicantia of pregnant, lactating1, and ' resting' females plotted to a time scale so as to represent two sexual cycles. See text for explanation. The mean size of the largest corpus albicans in lactating females is 5-58 cm.; the mean size of the largest corpus albicans in lactating females which are also pregnant (not given in Table 20) is 5-61 cm., and in' resting' females it is 5-57 cm. These mean sizes are not significantly different, and if we suppose that there has been not more than one post-partum ovulation in lactating pregnant females, then their largest corpus albicans must represent the corpus luteum of the previous pregnancy. The largest corpus albicans in non-pregnant lactating females and resting females is presumed (because of its closely similar size) also to represent the previous corpus luteum of pregnancy. In pregnant females the largest corpus albicans must either represent the corpus luteum of the previous pregnancy, or an unsuccessful ovulation before the current pregnancy. The latter case is unlikely, because it would mean that the second largest corpus albicans of pregnant females represents the largest corpus albicans of resting females, and has undergone rapid regression. It would also mean that the fin whale is polyoestrous, with on average two ovulations in the breeding season, the second of which leads to pregnancy, whereas the evidence points to a seasonally monoestrous cycle. 1 The lactating females are in late lactation (p. 445), so close to the resting stage.
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