THE HUMPBACK WHALE 71 



As in other rorquals, growth in length continues after sexual maturity is reached, and 

 does not stop until the epiphyses of the vertebrae are fused to the bodies. z\nkylosis 

 of the epiphyses takes place first at each end of the vertebral column and later in its 

 middle part. The results of the examination of a few vertebral columns are shown in 

 Table XXII. In this table also the numbers of different ages of scars present on the 

 skin are recorded, as also is the age, in breeding seasons, of the females. The age in years 

 can only be given in the case of females in their first breeding season and in them it is 

 one and a half to two years. 



The oldest whale appears to be no. 3426, in which all the epiphyses were ankylosed 

 and which had twenty-one corpora lutea in its ovaries. If its breeding seasons had been 

 spaced at every two years this whale would be ten years old, but some of the seasons may 

 have been spaced at only eighteen-month intervals, in which case its age would be less 

 than ten years. If it had bred as frequently as possible, that is, twice every three years, 

 it would be eight years old. However, it may safely be said that growth is complete and 

 the epiphyses are fused by the age of ten years and may be so before that age is reached. 

 Hinton (1925) states "complete fusion is, perhaps, to be regarded as a sign of middle 

 age, if not of senility ". If fusion is complete at ten years of age the former alternative 

 would appear the more likely. Whales nos. 3206 and 3573 were both in their third 

 breeding season, but 3206 was much nearer physical maturity than 3573 : the posterior 

 lumbar epiphyses were ankylosed and the anterior and thoracic ones, though not 

 ankylosed, were separated from the bodies of the vertebrae by thin cartilage only, 

 whereas in 3573 none of the epiphyses were ankylosed and all were separated from the 

 vertebral bodies by thick cartilage. Here again the difference may be due to one or more 

 of the past breeding seasons of whale no. 3573 being spaced at only eighteen-month 

 intervals from the preceding ones, thus making its number of breeding seasons equal to 

 that of no. 3206, though its duration of life had been shorter. 



The particulars of surface scars recorded in Table XXII show that data regarding the 

 amount of scarring visible are too scanty to give any indication of the age of the whale, 

 because the older scars become very confused and partly obliterated. 



Two direct observations on the length of life of Humpback whales are recorded by 

 Ommanney (1933). Both occurred in New Zealand waters and were due to the recovery 

 of harpoons, of types that were clearly recognizable, after intervals of eighteen and seven 

 years respectively, in the same localities in which they were lost. 



Referring now to Tables V, VI, VII and VIII, which show (in roman type) the values 

 of the measurements of different parts of the body according to the length of the 

 whale, an indication of the relative rates of growth of the various parts may be obtained. 

 If the mean values of the various measurements are plotted against the total length of 

 the whale on a double logarithmic scale the results shown in Figs. 62-78 are obtained. 

 Measurements of the South Georgia whales only are used, and the values for males and 

 females are distinct. In each of these figures, even though they are constructed from 

 scanty data, the points are obviously falling about a straight line, and in some of them 

 the approximation is very close. This being so it may be taken that the rates of 



