. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. 346 DISCOVERY REPORTS Table 2. Immature fin whale females approaching puberty: mean maximum follicle diameters Mean max. follicle size (mm.) Size of , ^ Month sample Monthly Grouped January 20 io-8 — 2-25 February 14 io-6 — 171 March 12 5-0 — t April 3 6-ol s May 2 6-oj o-o 269 June July 2 29-51 1 3o-oJ 29-66 2-12 August* 4 32-5 — 2-I7 October 1 25-01 3 33-oJ November 31-25 S-69 * 61-63 ft- in length. f The March sample values are all recorded as about 5 mm. 70 60 50 a 40 O 30 y 20 10. IMMA
. Discovery reports. Discovery (Ship); Scientific expeditions; Ocean; Antarctica; Falkland Islands. 346 DISCOVERY REPORTS Table 2. Immature fin whale females approaching puberty: mean maximum follicle diameters Mean max. follicle size (mm.) Size of , ^ Month sample Monthly Grouped January 20 io-8 — 2-25 February 14 io-6 — 171 March 12 5-0 — t April 3 6-ol s May 2 6-oj o-o 269 June July 2 29-51 1 3o-oJ 29-66 2-12 August* 4 32-5 — 2-I7 October 1 25-01 3 33-oJ November 31-25 S-69 * 61-63 ft- in length. f The March sample values are all recorded as about 5 mm. 70 60 50 a 40 O 30 y 20 10. IMMATURE NON-PREGNANT PREGNANT 4 S 6 DIAMETER IN CMS. 10 Text-fig. 2. Frequency distributions of maximum follicle diameters. that these were maturing follicles, but they may have reached a stage of development at which regres- sion was about to begin. Mackintosh and Wheeler (1929) showed that the size of the largest follicle in female fin whales approaching puberty increased from a minimum in January-April, to about 3 cm. in June and July. There are in the present material 62 pairs of ovaries from immature females which were approaching puberty (defined as females over 63 ft. in length, except for four immature females taken at Durban which were 61-63 ft. in length). In Text-fig. 3 the means and variation of seven samples from January, February, March, April and May combined, June and July combined, August, October and November combined, are presented. The June/July sample is from Saldanha Bay, South Africa, and the August sample is from Durban, South Africa. Although the size of the critical samples is small, this evidence suggests that there is a follicular cycle showing one or more peaks from June to November or December, when the maximum follicle size is about 3 cm. or more, and minimum values between December (or January) and May, when the maximum follicle size is about 1 cm. or less. The absolute maximum size, from an immature female taken in November, was about 5 cm.
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