THE AGE OF FEMALE BLUE WHALES 



255 



general trend of frequencies. The method adopted was to take the frequencies in groups 

 of three, add them together, and obtain the mean. For instance, the number of occur- 

 rences of one, two, and three corpora lutea were added together and divided by three. 

 Then the numbers for two, three, and four; three, four, and five, were treated in the 



O ACTUAL FREQUENCIES 



1934-35 



1935 -3G 



5 10 15 20 25 30 35. 5 10 15 20 25 30 



NUMBER OF CORPORA LUTEA 



Fig. 9. Smoothed corpora lutea frequencies, aggregate, 1934-5 an ^ : 935~6. 



same way, and so on. Each frequency comes into the calculations thrice and a consider- 

 able smoothing effect is obtained, which eliminates the fluctuations due to faulty 

 sampling and possible individual variations while preserving the real trend of the fre- 

 quencies. Only those ovaries with one or more corpora lutea have been included, since 

 this part of the discussion is confined to definitely mature whales. 



