136 



DISCOVERY REPORTS 



the averages for the third group on the left, the diagram shown in Fig. 40 is produced. 

 From this diagram the length of the period of gestation may be deduced as about 

 16 months. If the line from Fig. 40 is now superimposed on Fig. 39 it is found that the 



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Apr Mau June JuIl| Aug" Sep 



Fig. 39. Sperm whale. Foetal lengths by months. 



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points extend on each side of the line for about 3^ months, so that if lines are drawn 

 parallel to the average line, and at that distance from it on each side, the diagram in 

 Fig. 41 is produced, which shows a breeding season in which pairing extends over 



