260 



DISCOVERY REPORTS 



place at ten to eleven years of age (i.e. 1-91 corpora lutea accumulated in third year from 

 birth plus eight years at an average increment of 1-13 per annum). Wheeler (1930) 

 found the age of Fin whales at physical maturity to be between six and eight years 

 (p. 417). Blue whales would appear to take rather longer to reach maturity, which seems 

 reasonable since they grow to greater lengths than Fin whales. 



The determination of the age of Blue females at physical maturity is of great im- 

 portance from the economic point of view, since the data to be derived from this could 

 not fail to be of assistance in assessing the age composition of the catch. It would not be 

 impossible for a simple examination of the thoracic vertebrae to be carried out by 

 whalers during the dismemberment of the whales. The data resulting from this exami- 

 nation would be a guide only to the number of whales in the catch which were past 

 complete physical maturity, and would not furnish a complete age distribution. The 

 results would however be valuable in the study of the composition of the catch through 

 several successive years. 



PRESENT SPAN OF LIFE 



As shown above we have no data which will indicate the age of the very oldest whale 

 which might live in the sea under normal conditions. One is justified in referring to the 

 present situation as abnormal if only because of the very high proportion of immature 

 whales taken (p. 266). While it would be of great interest to know how long a Blue 

 female can live, because of the widespread conjecture there has been on the subject, 

 it is perhaps not essential so long as we know the greatest age to which whales retain 

 their reproductive powers. The percentage of pregnant whales for the two seasons is 

 shown in the following table : 



o means 0%, — means no data. 



