NEWLY MATURE FEMALES 419 



This has been placed in December as a corpus luteum of ovulation and in January as a corpus 

 albicans. 



The paucity of records in the early months does not permit a precise estimate of the peak time of 

 ovulation during this period, and the purpose is merely to show that there is an ovulatory period in 

 this group of pubertal females which is well outside the main breeding period (see also pp. 403-6), 

 From the evidence presented in Text-fig. 40, it is presumed that before January the majority of 

 pubertal females present in the Antarctic have recently ovulated, and that after January the ovaries of 

 the majority contain young regressing corpora albicantia from recent ovulations. This evidence also 

 suggests that an ovulatory period is associated with the southern migration which probably takes place 

 in the majority of this group in November, December, and January, but may be slightly earlier or 

 later. 



Table 16. Monthly frequency of ovulation of pubertal female fin whales taken in the antarctic 



Corpus albicans 



No. 



Percentage 



30( + i*) 

 * This record has been included as corpus luteum and corpus albicans; see text p. 418. 



One anomalous pubertal female has not been included in Text-fig. 40, a, for reasons given below, 

 but is included in Text-fig. 40, b. This individual was taken on 24 January and had one corpus 

 aberrans in each ovary (see p. 380), measuring 2-5 and 2-3 cm. in diameter. The largest follicle was 

 3-5 cm. in diameter and there were several follicles about 3 cm. in size, in each ovary. This female 

 had not yet acquired a diatom film and is, therefore, presumed to have recently completed a southern 

 migration during which ovulations took place which led to the formation of corpora aberrantia. It 

 does not invalidate the conclusions put forward above. 



The monthly variation in size of the largest follicle in the ovaries of females approaching puberty 

 (over 63 ft. in length) has been discussed above (p. 346, Table 2, Text-fig. 3). In conjunction with the 

 foregoing evidence it is significant that the largest follicles are found in females of this group taken 

 in the Antarctic in November. The mean size of the largest follicle in three individuals taken in 

 November is 3-3 cm., and the absolute maximum size of follicles in immature females was about 5 cm. 

 for one of these November animals. From January to May the monthly mean maximal follicle size 

 is about 1 cm. or less. The large size of the November follicles suggests pro-oestrus enlargement which 

 might or might not have been followed by maturation and ovulation. 



For the present it is sufficient to show that ovulations can occur outside the recognized pairing 

 season, and that then also there is a single ovulation, almost invariably unsuccessful probably because 

 the majority of males are not then in breeding condition. There is no evidence for a succession of 

 several ovulations at intervals of a month or less. The evidence presented below (p. 438) suggests that 

 this is also true of multiparous females which ovulate outside the usual breeding season. 



One other separate piece of evidence which is inconclusive when considered alone, but which 

 appears to fit this hypothesis better than any other, remains to be discussed. In Text-fig. 41 the mean 

 length, plus or minus one standard deviation and two standard errors, is set out for two groups of newly 



