THE SEI WHALE 187 



Turning first to the data relating to foetuses, there are records of fifty-five foetuses 

 examined by the Discovery staff and of an additional fourteen in the British Museum 

 statistics. Of the total of sixty-nine foetuses forty-five were males and twenty-four 

 females, giving a proportion of 65-3 per cent of males. The data are further analysed in 

 Table III which shows the proportions of the sexes for each metre of total length. The 

 proportion of males varies from 50-0 to 83-4 per cent with an average of 63-9 per cent. 



Table III. Sei whale. Sex of foetuses 



Table IV. Sei whale. Sex ratio 



Coming now to the whales and examining them similarly for each metre of total 

 length, the result shown in Table IV is obtained. Ignoring the class of lo-ii m. total 

 length, in which there is only one record, it is seen that up to a total length of 15 m. 

 the proportion of males varies from 76-5 to 45-5 per cent with an average of 61 -i percent. 

 The total number of whales up to 15 m. in total length is eighty-four, of which forty-nine 

 were males and thirty-five females, giving a proportion of 58-4 per cent of males. 



Up to a total length of 15m., therefore, the sex ratio of the whales is similar to 

 that of the foetuses, namely, 58-4 per cent of males compared with 65-3 per cent for 

 foetuses, with average percentages for each metre of total length of 61 -i and 63-9 

 per cent respectively. The sex ratio below 15 m. of total length may thus be said to be 



