BREEDING AND LIFE CYCLE 265 



ment neglects the abnormally large volume, 5-5 1., of the testes of the longest whale judged immature.) 

 Whales may be considered immature if the combined volumes of their testes are less than i-o 1. The 

 maturity of those with intermediate testis volumes should be left in doubt. 



Table 19. Females. Lengths of sexually mature and immature whales examined 

 at Horta from 1949 to 1954. The larger mature whales are omitted 



Mature 



Lenqth in metres 



Fig. 5. Females. Length of body and weight of ovaries in non-pregnant whales 

 examined at Horta from 1949 to 1954. 



Sexual maturity in female sperm whales has been investigated by examining pairs of ovaries 

 collected from 165 whales at Horta between 1949 and 1954. Ovaries from sixteen whales bore no 

 corpora lutea, either functional or regressed, and so were immature. From Table 19 it is seen that 

 females become mature within the range 7-9 to 9-5 m. (26 to 31 ft.). The data, so far as they go, 

 indicate 8-8 m. (29 ft.) as the mean length at sexual maturity. 



Fig. 5 shows that any female with ovaries weighing 0-5 kg. or more may be expected to be mature. 



