AGE EVIDENCE FROM CORPORA LUTEA 411 



2766) were captured and brought to the station on the same day. They were of the 

 same length (22-5 m.), but one possessed twenty-four old corpora lutea and a functional 

 corpus luteum (pseudo-pregnancy); the other had one old corpus luteum and one of 

 pregnancy. In the former, ankylosis of the epiphyses throughout the vertebral column 

 showed that complete physical maturity had been reached ; in the latter, thick cartilaginous 

 layers still separated the epiphyses from their centra. 



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18 19 ' 20 21 ' 22 23 24 



LENGTH OF WHALE IN METRES 



Fig. 2. Fin whales, females: Season 1929-30. Length of whale and number of corpora lutea. 

 O Epiphyses not ankylosed throughout column. • Epiphyses ankylosed throughout. 



If the numbers of corpora lutea are plotted against the corresponding lengths of the 

 whales, and the physically mature whales distinguished from those not mature (Fig. 2), 

 it is readily seen that physical maturity bears little relation to length, but does bear a 

 relation to the number of corpora lutea. Indeed, of 105 whales with less than fifteen 

 corpora lutea only two, with eleven and twelve respectively, were physically mature; 

 while of 66 whales with more than fifteen corpora lutea only four, with sixteen, 

 sixteen, twenty and twenty-one, were physically immature. 



The age at physical maturity is thus the number of years occupied in the accumula- 

 tion of fifteen corpora lutea in the ovaries plus the two years that elapse between birth 

 and sexual maturity. 



One of the applications of this result is that if the number of corpora lutea has been 

 noted, comparisons can be made between the number of physically mature whales 

 caught in different seasons and areas. This applies particularly to our own previous 



