SOUTHERN RIGHT WHALE 179 



ovary are likely to have been those of unsuccessful dioestrous cycles in the same sexual 

 season. If the sexual season in this species thus consists of about three dioestrous cycles 

 and four ovulations, the other nine old corpora lutea in the ovaries represent at least 

 two previous pregnancies. They probably actually represent three previous pregnancies, 

 because in all other species of vv^hale in which the sexual cycle is known, the first sexual 

 season usually consists of one ovulation only and dioestrous cycles do not occur until 

 the second and subsequent sexual seasons. The nine old corpora lutea would thus re- 

 present one ovulation for the first pregnancy, and four for each of the subsequent ones, 

 and the calf that was killed with this whale would have been her fourth. 



Whale No. 3560 had been pregnant at least once before, as is shown by the mammary 

 gland, which was involuted after functional activity. The ovaries contained four old 

 corpora lutea, and if the first pregnancy was represented by one only, the other three 

 would represent a second pregnancy, and the probability is in favour of the latter 

 suggestion. 



According to Millais (1906) the Northern Right whale bears a young one once every 

 two years and suckles it for twelve months. The present series of whales gives no in- 

 formation on this subject, but if the period of gestation is comparable to that in other 

 whales there is no reason to think that they breed oftener than once every two years, 

 though the period of lactation mentioned seems excessive. There appears, however, to 

 be a period of anoestrus between lactation and the next pregnancy judging from the 

 resting ovaries of whale No. 3560; but the presence of a follicle already 15 mm. in 

 diameter in one of the ovaries of whale No. 1019, while she was still in full lactation, 

 points to the probability that this period is of short duration. 



The nipples lie on either side of the cloacal groove and are situated within short 

 mammary grooves, with small subsidiary grooves bordering them (Plate XII, fig. 2; 

 Plate XVI, fig. i). In whale No. 3560 they were situated 25 cm. on each side of the 

 centre of the genital groove. 



The mammary gland in whale No. 3560, which was involuted after functional ac- 

 tivity, measured 35 cm. in length and 7 cm. in thickness. That of whale No. 1019, which 

 was in full lactation, was 25 cm. thick. The teats in this whale were everted and milk was 

 running from them (Plate XII, fig. 2). 



MATURITY 



Three of these whales were obviously sexually mature, Nos. 503 (male) and 1019 and 

 3560 (females). The vertebral column was examined in only one of these. No. 3560, 

 which had been pregnant at least once and probably twice. In it the epiphyses were 

 unfused throughout the vertebral column, showing that the species, like all the other 

 large whales, reaches sexual maturity long before it reaches physical maturity. 



OTHER NOTES 

 For whale No. 1020, the calf of No. 1019, there are the following additional notes: 

 Length of eye slit, 12 cm. 



