THE AGE OF FEMALE BLUE WHALES 



245 



supposed, therefore, to be a fairer sample. Yet in the latter collections there are a 

 number of ovaries purporting to come from whales 78-81 ft. long and showing a large 

 range of corpora lutea numbers up to twenty-nine. I feel convinced that some error 

 has occurred. 



I found no whales of 79-81 ft. with more than seven corpora lutea in 1932-3, but if a 

 greater number were properly associated with this length range the fact would emerge 

 without fail in any reasonably large sample. Again, if a whale could ovulate any number 

 of times up to twenty-nine before reaching a length of 81 ft. it might easily have 

 accumulated 100 or more corpora lutea by the time it grew to, say, 86 ft., since old 

 corpora are known to persist. As will be seen in the corpora lutea frequencies for 

 two seasons, there is a definite cessation of numbers at thirty-four corpora in the first 

 season and twenty-eight in the second. The chances of large numbers of corpora lutea 

 occurring through multiple ovulations are too small to be of importance ; twin or triple 

 corpora lutea are found in less than 1 per cent of the total adult ovaries examined. 



A table of the questionable ovaries is here given: 



The fact that the percentage of small whales with large numbers of corpora lutea 

 varies from ship to ship confirms the opinion that some mistake has been made. If these 

 whales occur at all they would be found by all factory ships. 



It has been decided, therefore, on all grounds to exclude from the calculations those 

 ovaries which were stated to have come from whales up to 81 ft. long and which showed 

 more than seven corpora lutea. The results of personal examination have been taken as 

 the criterion. 



The table overleaf based on the corrected figures shows the average number of 

 corpora lutea found in whales of each unit of length from 78 to 83 ft. Two collections 

 (547 and 464 whales respectively) are considered separately in order to show how far 

 the results are consistent from one year to another. 



The sharp increase in the average number of corpora lutea at 82 ft. suggests that 

 whales of 78-81 ft. belong to one age group and that whales of 82 ft. and higher lengths 

 belong to later year groups. There seems to be little doubt that the age distinction 

 between 78-81 ft. whales and those of greater lengths is valid, since the difference 

 is so marked. The distinction did not appear in the 1932-3 results, probably because 



